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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
MAY 2007 REV. 1.0.0
GENERAL DESCRIPTION
The XR19L222 (L222) is a highly integrated device that combines a full-featured two channel Universal Asynchronous Receiver and Transmitter (UART) and RS232 transceivers. The L222 is designed to operate with a single 3.3V or 5V power supply. The L222 is fully compliant with EIA/TIA-232-F Standards from a +3.3V to +5.5V power supply. The device operates at 1 Mbps data rate with worst case 3K ohms load. Both RS-232 driver outputs and receiver inputs can operate in harsh electrical environments of +/-15V without damage and can survive multiple +/-15kV ESD on the RS-232 lines, while maintaining RS-232 output levels. The L222 operates in four different modes: Active, Partial Sleep, Full Sleep and Power-Save. Each mode can be invoked via hardware or software. Upon power-up, the L222 is in the Active mode where the UART and RS-232 transceiver function normally. In the Partial Sleep mode, the internal crystal oscillator of the UART or charge pump of the RS-232 transceiver is turned off. In Full Sleep mode, both the crystal oscillator and the charge pump are turned off. While the UART is in the Sleep mode, the Power-Save mode isolates the core logic from the control signals (chip select, read/write strobes, address and data bus lines) to minimize the power consumption. The RS-232 receivers remain active in any of these four modes.
APPLICATIONS
* Battery-Powered Equipment * Handheld and Mobile Devices * Handheld Terminals * Industrial Peripheral Interfaces * Point-of-Sale (POS) Systems
FEATURES
* Meets true EIA/TIA-232-F Standards from +3.3V to +5.5V
operation
* Up to 1 Mbps data transmission rate * 45us sleep mode exit (charge pump to full power) * ESD protection for RS-232 I/O pins at

+/-15kV - Human Body Model +/-15kV - 61000-4-2, Air-Gap Discharge +/- 8kV - 61000-4-2, Contact Discharge
* Software compatible with industry standard 16550 UART * Intel/Motorola bus select * Complete modem interface * Sleep and Power-save modes to conserve battery power * Wake-up interrupt upon exiting low power modes
FIGURE 1. BLOCK DIAGRAM
VCC (3.3 to 5.5V)
XTAL1
XTAL2
R_EN
GND
FAST
ACP
C2+
C1+
C2-
C1-
*5 V Tolerant Inputs
VREF+ Crystal Osc/Buffer BRG TXA RXA
5K
PwrSave A2:A0 D7:D0 IOR# IOW# (R/W#) CSA# (CS#) CSB# INTA (IRQ#) INTB RESET (RESET#) Intel or Motorola Bus Interface
Charge Pump VREFTXDA RXDA RTSA DTRA CTSA DSRA RIA CDA CDB RIB DSRB CTSB DTRB RTSB TXDB TXB RXDB RXB
UART Registers
64 Byte TX & RX FIFO
RTSA# DTRA# CTSA#
5K
Modem I/Os
DSRA#
5K
RIA#
5K
CDA# Channel A CDB# RIB# DSRB# CTSB# DTRB# RTSB# TXB RXB
Ch A Transceiver
5K
Channel B I/M#
Channel B Transceiver
RXBSEL UART XR19L222
(See Figure 6)
RS-232 Transceiver
Exar Corporation 48720 Kato Road, Fremont CA, 94538 * (510) 668-7000 * FAX (510) 668-7017 * www.exar.com
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER FIGURE 2. PIN OUT OF THE DEVICE
54 VCC 56 C3B 55 C3A 53 VREF+ 62 CDB 61 CDA 60 RIA 52 C1+
REV. 1.0.0
51 C1-
50 NC 49 NC
57 D0
64 D4 63 D3
59 D2
58 D1
CTSA GND CTSB RTSB D5 D6 D7 RXBSEL RXB TXB CSA# CSB# DTRB
1 2 3 4 5 6 7 8 9 10 11 12 13
48 47 46 45 44
VCC RESET C2+ C2TXDA INTA INTB DTRA DSRA A0 A1 A2 RXDA GND NC NC
XR19L222 64-pin QFN Intel Bus Mode
43 42 41 40 39 38 37 36 35 34 33 RTSA 31 RXDB 32 I/M# 30
PWRSAVE 14 RIB 15 DSRB 16 R_EN 24 ACP 25 NC 26 VREF- 27 XTAL2 19 IOW# 20 XTAL1 18 NC 28 TXDB 29 FAST 21 GND 22 IOR# 23 GND 17
VCC
54 VCC
56 C3B
55 C3A
53 VREF+
62 CDB
61 CDA 60 RIA
52 C1+
51 C1-
50 NC 49 NC
57 D0
64 D4 63 D3
59 D2
58 D1
CTSA GND CTSB RTSB D5 D6 D7
1 2 3 4 5 6 7
48 47 46 45 44
VCC RESET# C2+ C2TXDA IRQ# NC DTRA DSRA A0 A1 A2 RXDA GND NC NC
RXBSEL 8 RXB 9 TXB 10 CS# 11 A3 12 DTRB 13 PWRSAVE 14 RIB 15 DSRB 16
XR19L222 64-pin QFN Motorola Bus Mode
43 42 41 40 39 38 37 36 35 34 33 RTSA 31
VREF- 27
XTAL2 19 R/W# 20
XTAL1 18
ORDERING INFORMATION
PART NUMBER XR19L222IL64 PACKAGE 64-pin QFN OPERATING TEMPERATURE RANGE -40C to +85C DEVICE STATUS Active
2
RXDB 32 GND
R_EN 24 ACP 25
NC 26
NC 28 TXDB 29
FAST 21
GND 22
NC 23
GND 17
I/M# 30
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
PIN DESCRIPTIONS
Pin Descriptions
NAME 64-QFN PIN# TYPE DESCRIPTION
DATA BUS INTERFACE (CMOS/TTL Voltage Levels) A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 IOR# (NC) 37 38 39 7 6 5 64 63 59 58 57 23 I Address bus lines [2:0]. These 3 address lines select one of the internal registers in the UART during a data bus transaction. Data bus lines [7:0] (bidirectional).
I/O
I
When I/M# pin is HIGH, the Intel bus interface is selected and this input becomes read strobe (active LOW). The falling edge instigates an internal read cycle and retrieves the data byte from an internal register pointed by the address lines [A2:A0], puts the data byte on the data bus to allow the host processor to read it on the rising edge. When I/M# pin is LOW, the Motorola bus interface is selected and this input is not used. When I/M# pin is HIGH, it selects Intel bus interface and this input becomes write strobe (active LOW). The falling edge instigates the internal write cycle and the rising edge transfers the data byte on the data bus to an internal register pointed by the address lines. When I/M# pin is LOW, the Motorola bus interface is selected and this input becomes read (HIGH) and write (LOW) signal. When I/M# pin is HIGH, this input is chip select A (active low) to enable channel A in the device. When I/M# pin is LOW, this input becomes the chip select (active low) for the Motorola bus interface. When I/M# pin is HIGH, this input is chip select B (active low) to enable channel B in the device. When I/M# pin is LOW, this input becomes address line A3 which is used for channel selection in the Motorola bus interface. Input logic 0 selects channel A and logic 1 selects channel B.
IOW# (R/W#)
20
I
CSA# (CS#)
11
I
CSB# (A3)
12
I
INTA (IRQ#)
43
O When I/M# pin is HIGH, it selects Intel bus interface and this output become the active (OD) HIGH device interrupt output for channel A. This output is enabled through the software setting of MCR[3]: set to the active mode when MCR[3] is set to a logic 1, and set to the three state mode when MCR[3] is set to a logic 0. See MCR[3]. When I/M# pin is LOW, it selects Motorola bus interface and this output becomes the active LOW, open-drain interrupt output for both channels. An external pull-up resistor is required for proper operation. MCR[3] must be set to a logic 0 for proper operation of the interrupt. O When I/M# pin is HIGH, it selects Intel bus interface and this output become the active (OD) HIGH device interrupt output for channel B. This output is enabled through the software setting of MCR[3]: set to the active mode when MCR[3] is set to a logic 1, and set to the three state mode when MCR[3] is set to a logic 0. See MCR[3]. When I/M# pin is LOW, it selects Motorola bus interface and this output is not used and can be left unconnected.
INTB (NC)
42
3
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER Pin Descriptions
NAME 64-QFN PIN# TYPE DESCRIPTION
REV. 1.0.0
MODEM OR SERIAL I/O INTERFACE (EIA-232/RS-232 Voltage Levels) TXDA RXDA RTSA CTSA 44 36 31 1 O I O I UART Channel A Transmit Data. The TX signal will be LOW (< 1.5V) during reset or idle (no data). UART Channel A Receive Data. The RX data input must idle LOW (< 1.5V). This input has an internal pull-down resistor and can be left unconnected when not used. UART Channel A Request-to-Send or general purpose outputs. These outputs must be asserted prior to using auto RTS flow control, see EFR[6], MCR[1] and IER[6]. UART Channel A Clear-to-Send or general purpose inputs. It can be used for auto CTS flow control, see EFR[7], MSR[4] and IER[7]. This input has an internal pull-down resistor and can be left unconnected when not used. UART Channel A Data-Terminal-Ready or general purpose outputs. UART Channel A Data-Set-Ready or general purpose inputs. This input has an internal pulldown resistor and can be left unconnected when not used. UART Channel A Carrier-Detect or general purpose inputs. This input has an internal pulldown resistor and can be left unconnected when not used. UART Channel A Ring-Indicator or general purpose inputs. This input has an internal pulldown resistor and can be left unconnected when not used. UART Channel B Transmit Data. The TX signal will be LOW (< 1.5V) during reset or idle (no data). UART Channel B Receive Data. RXDB will be the input signal to the internal UART when RXBSEL is LOW. If RXB is used, then RXBSEL should be HIGH. The RX data input must idle LOW (< 1.5V). This input has an internal pull-down resistor and can be left unconnected when not used. UART Channel B Request-to-Send or general purpose outputs. These outputs must be asserted prior to using auto RTS flow control, see EFR[6], MCR[1] and IER[6]. UARTChannel B Clear-to-Send or general purpose inputs. It can be used for auto CTS flow control, see EFR[7], MSR[4] and IER[7]. This input has an internal pull-down resistor and can be left unconnected when not used. UART Channel B Data-Terminal-Ready or general purpose outputs. UART Channel B Data-Set-Ready or general purpose inputs. This input has an internal pulldown resistor and can be left unconnected when not used. UART Channel B Carrier-Detect or general purpose inputs. This input has an internal pulldown resistor and can be left unconnected when not used. UART Channel B Ring-Indicator or general purpose inputs. This input has an internal pulldown resistor and can be left unconnected when not used.
DTRA DSRA CDA RIA TXDB RXDB
41 40 61 60 29 32
O I I I O I
RTSB CTSB
4 3
O I
DTRB DSRB CDB RIB
13 16 62 15
O I I I
SERIAL I/O INTERFACE (CMOS/TTL Voltage Levels) TXB RXB 10 9 O I UART Channel B Transmit data. This is the TXB output signal from the UART. This pin can be used to communicate with an external Infrared or RS-422 transceiver if TXDB is unused. UART Channel B Receive data. This is the RXB input signal to the UART. If RXDB is not used (RXBSEL is HIGH), then this pin can be used to communicate with an external Infrared or RS-422 transceiver. If RXDB is used (RXBSEL is LOW), this pin should be left open.
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XR19L222
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
Pin Descriptions
NAME 64-QFN PIN# TYPE DESCRIPTION
ANCILLARY SIGNALS (CMOS/TTL Voltage Levels) XTAL1 XTAL2 PwrSave 18 19 14 I O I Crystal or external clock input. This input is not 5V tolerant. Crystal or buffered clock output. This output may be use to drive a clock buffer which can drive other device(s). Power-Save (active high). This feature isolates the L222's data bus interface from the host preventing other bus activities that cause higher power drain during sleep mode. See Sleep Mode with Auto Wake-up and Power-Save Feature section for details. Autosleep for Charge Pump (active HIGH). When this pin is HIGH, the charge pump is shut off if the L222 is already in partial sleep mode, i.e. the crystal oscillator is stopped. See
ACP
25
I
"Section 2.18, Sleep Modes and Power-Save Feature with Wake-Up Interrupt" on page 20.
I/M# 30 I Intel or Motorola Bus Select. When I/M# pin is HIGH, 16 or Intel Mode, the device will operate in the Intel bus type of interface. When I/M# pin is LOW, 68 or Motorola mode, the device will operate in the Motorola bus type of interface. When I/M# pin is HIGH for Intel bus interface, this input becomes RESET (active high). When I/M# pin is LOW for Motorola bus interface, this input becomes RESET# (active low). A 40 ns minimum active pulse on this pin will reset the internal registers and all outputs of the UART. The UART transmitter output will be held HIGH, the receiver input will be ignored and outputs are reset during reset period (see Table 16). Charge pump capacitors. As shown in Figure 1, a 0.1 uF capacitor should be placed between these 2 pins. Charge pump capacitors. As shown in Figure 1, a 0.1 uF capacitor should be placed between these 2 pins.
RESET (RESET#)
47
I
C2+ C2C1+ C1VREF+ VREFR_EN
46 45 52 51 53 27 24
-
-
Pwr +5.0V generated by the charge pump. Pwr -5.0V generated by the charge pump. I When the supply voltage is < 3.6V, connect R_EN to GND. When the supply voltage is > 3.6V, connect R_EN to VCC. When the supply voltage is 3.3 V, C3A and C3B should be connected to VCC. When the supply voltage is 5 V, C3A should be connected to C3B with a 1 uF capacitor to GND. When RXBSEL is HIGH, RXB is the input to the receiver of the UART. When RXBSEL is LOW, RXDB is the input to the receiver of the UART. When FAST is HIGH, the maximum serial data rate is 1 Mbps. When FAST is LOW, the maximum serial data rate is 250 Kbps.
C3A C3B RXBSEL
55 56 8
I
I
FAST
21
I
VCC GND
48, 54
Pwr 3.3V to 5.5V power supply. All CMOS/TTL input pins, except XTAL1, are 5V tolerant.
2, 17, 22, Pwr Power supply common, ground. 35
5
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER Pin Descriptions
NAME 64-QFN PIN# PAD TYPE DESCRIPTION
REV. 1.0.0
Pwr The center pad on the backside of the 64-QFN package is metallic and is not electrically connected to anything inside the device. It must be soldered on to the PCB and may be optionally connected to GND on the PCB. The thermal pad size on the PCB should be the approximate size of this center pad and should be solder mask defined. The solder mask opening should be at least 0.0025" inwards from the edge of the PCB thermal pad. No Connect. Note that in Motorola mode, the IOR# pin also becomes an NC pin.
NC
26, 28, 33, 34, 49, 50
NOTE: Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain. For CMOS/TTL Voltage levels, 'LOW' indicates a voltage in the range 0V to VIL and 'HIGH" indicates a voltage in the range VIH to VCC. For RS-232 Voltage levels, 'LOW' is any voltage < 1.5V and 'HIGH' is any voltage > 3V.
6
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
1.0 PRODUCT DESCRIPTION The XR19L222 consists of a two-channel UART and RS-232 transceivers. It operates from a single +3V to 5.5V supply with data rates up to 1Mbps, while meeting all EIA RS-232F specifications. Its feature set is fully compatible to the XR16V2751 device. Unlike the XR16V2751, most of the modem signals are not CMOS/TTL level, but conform to EIA/TIA 232 or RS-232 voltage levels. The only two signals that are CMOS/TTL level are the TXB and RXB signals. They can be used with an external IR or RS-422 transceiver when their corresponding RS-232 signals, TXDB and RXDB, are not used. The configuration register set is 16550 UART compatible for control, status and data transfer. Also, the L222 has 64-bytes of transmit and receive FIFOs, automatic RTS/CTS hardware flow control, automatic Xon/Xoff and special character software flow control, transmit and receive FIFO trigger levels, and a programmable fractional baud rate generator with a prescaler of divide by 1 or 4. Additionally, the L222 includes the ACP pin which the user can shut down the charge pump for the RS-232 drivers. In the UART portion, the Power-Save feature isolates the databus interface to further reduce power consumption in the Sleep mode. The L222 is fabricated using an advanced CMOS process. Enhanced Features The L222 UART provides a solution that supports 64 bytes of transmit and receive FIFO. Increased performance is realized in the L222 by the transmit and receive FIFOs, FIFO trigger level controls and automatic flow control mechanism. This allows the external processor to handle more networking tasks within a given time. This increases the service interval giving the external CPU additional time for other applications and reducing the overall UART interrupt servicing time. In addition, the L222 provides the ACP and PowerSave modes that drastically reduces the power consumption when the device is not used. The combination of the above greatly reduces the CPU's bandwidth requirement, increases performance, and reduces power consumption. Intel or Motorola Data Bus Interface The L222 provides a host interface that supports Intel or Motorola microprocessor (CPU) data bus interface. The Intel bus compatible interface allows direct interconnect to Intel compatible type of CPUs using IOR#, IOW# and CS# inputs for data bus operation. The Motorola bus compatible interface instead uses the R/W# and CS# signals for data bus transactions. See pin description section for details on all the control signals. The Intel and Motorola bus interface selection is made through the pin, I/M#. Data Rate The L222 is capable of operation up to 1 Mbps data rate. The UART section can operate at much higher speeds, but the speed of the RS-232 transceiver is limited to 1 Mbps. The device can operate either with a crystal on pins XTAL1 and XTAL2, or external clock source on XTAL1 pin. Internal Enhanced Register Sets The L222 UART has a set of enhanced registers providing control and monitoring functions. Interrupt enable/ disable and status, FIFO enable/disable, selectable TX and RX FIFO trigger levels, automatic hardware/ software flow control enable/disable, programmable baud rates, modem interface controls and status, sleep mode and infrared mode are all standard features. Following a power on reset or an external reset (and operating in 16 or Intel Mode), the registers defaults to the reset condition and is compatible with the XR16V2751. RS-232 Interface The L222 includes RS-232 drivers/receivers for the entire modem interface. This feature eliminates the need for an external RS-232 transceiver. The charge pump provides output voltages of +5V and -5V for its drivers over the 3.3V to 5.5V VCC supply voltage. The serial outputs TXD, RTS and DTR swing between -5V (inactive) and 5V (active) RS-232 voltage levels. The serial inputs RXD, CTS, DSR, CD and RI are RS-232 receivers and can take any voltage swing from -15V to +15V. The receivers are always active, even in Full Sleep and PowerSave modes. The RS-232 drivers guarantee a data rate of 1 Mbps even when fully loaded with 3Kohm in parallel with 1000pF load. All RS-232 drivers and receivers are protected to 15kV using the Human Body Model ground combination, 8kV using IEC 61000-4-2 Contact Discharge, and 15kV using IEC 61000-4-2 Air-Gap Discharge. For more information, send an e-mail to uarttechsupport@exar.com.
7
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 2.0 FUNCTIONAL DESCRIPTIONS 2.1 CPU Interface The CPU interface is 8 data bits wide with 3 address lines and control signals to execute data bus read and write transactions. The L222 data interface supports the Intel compatible types of CPUs and it is compatible to the industry standard 16C550 UART. No clock (oscillator nor external clock) is required to operate a data bus transaction. Each bus cycle is asynchronous using CS#, IOR# and IOW# or R/W# inputs. A typical data bus interconnection for Intel and Motorola mode is shown in Figure 3. FIGURE 3. XR19L222 TYPICAL INTEL/MOTOROLA DATA BUS INTERCONNECTIONS
REV. 1.0.0
D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 IOR# IOW# UART_CSA# UART_CSB# UART_INTA UART_INTB R_EN ACP RXBSEL PWRSAVE FAST UART_RESET
D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 IOR# IOW# CSA# CSB# INTA INTB R_EN ACP RXBSEL PWRSAVE FAST RESET
VCC TXDA RXDA DTRA RTSA CTSA DSRA CDA RIA
VCC
UART Channel A
Full RS-232 Interface
TXDB RXDB UART Channel B DTRB RTSB CTSB DSRB CDB RIB TXB RXB GND External IR or RS-422 Transceiver Full RS-232 Interface
Intel Data Bus Interconnections
D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3 VCC R/W# UART_CS# VCC UART_IRQ# (no connect) R_EN ACP RXBSEL FAST PWRSAVE UART_RESET
D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 CSB# IOR# IOW# CSA#
VCC TXDA RXDA DTRA RTSA CTSA DSRA CDA RIA
VCC
UART Channel A
Full RS-232 Interface
TXDB RXDB DTRB RTSB
INTA INTB R_EN ACP RXBSEL FAST PWRSAVE RESET
UART Channel B
CTSB DSRB CDB RIB TXB RXB GND
Full RS-232 Interface
External IR or RS-422 transceiver
Motorola Data Bus Interconnections
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XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
2.2
5-Volt Tolerant Inputs
The CMOS/TTL level inputs of the L222 can accept up to 5V inputs when operating at 3.3V. Note that the XTAL1 pin is not 5V tolerant when an external clock supply is used. 2.3 Device Hardware Reset The RESET or RESET# input resets the internal registers and the serial interface outputs in both channels to their default state (see Table 16). An active pulse of longer than 40 ns duration will be required to activate the reset function in the device. 2.4 Device Identification and Revision The XR19L222 provides a Device Identification code and a Device Revision code to distinguish the part from other devices and revisions. To read the identification code from the part, it is required to set the baud rate generator registers DLL and DLM both to 0x00. Now reading the content of the DLM will provide 0x01 to indicate functional compatibility with the XR16V2751 and reading the content of DLL will provide the revision of the part; for example, a reading of 0x01 means revision A. 2.5 Channel A and B Selection The XR19L222 provides the user with the capability to bi-directionally transfer information between an external CPU and an external serial communication device. During Intel Bus Mode (I/M# pin connected to VCC), a LOW on chip select pins, CSA# or CSB#, allows the user to select UART channel A or B to configure, send transmit data and/or unload receive data to/from the UART. Selecting both UARTs can be useful during power up initialization to write to the same internal registers, but do not attempt to read from both UARTs simultaneously. Individual channel select functions are shown in Table 1. TABLE 1: CHANNEL A AND B SELECT IN 16 MODE
CSA# 1 0 1 0 CSB# 1 1 0 0 FUNCTION UART de-selected Channel A selected Channel B selected Channel A and B selected
During Motorola Bus Mode (I/M# pin connected to GND), the package interface pins are configured for connection with Motorola and other popular microprocessor bus types. In this mode the XR19L222 decodes an additional address, A3, to select one of the UART ports. The A3 address decode function is used only when in the Motorola Bus Mode. See Table 2. TABLE 2: CHANNEL A AND B SELECT IN 68 MODE
CS# 1 0 0 A3 N/A 0 1 FUNCTION UART de-selected Channel A selected Channel B selected
2.6
Channel A and B Internal Registers
Each UART channel in the L222 has a set of enhanced registers for control, monitoring and data loading and unloading. The configuration register set is compatible to those already available in the standard single 16C550 and dual ST16C2550. These registers function as data holding registers (THR/RHR), interrupt status and control registers (ISR/IER), a FIFO control register (FCR), receive line status and control registers (LSR/ LCR), modem status and control registers (MSR/MCR), programmable data rate (clock) divisor registers (DLL/ DLM), and an user accessible Scratchpad register (SPR).
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
REV. 1.0.0
Beyond the general 16C2550 features and capabilities, the L222 offers enhanced feature registers just like the XR16V2751, namely, EFR, Xon/Xoff 1, Xon/Xoff 2, FCTR, TRG, EMSR and FC that provide automatic RTS and CTS hardware flow control, Xon/Xoff software flow control, FIFO trigger level control and FIFO level counters. All the register functions are discussed in full detail later in "Section 3.0, UART INTERNAL REGISTERS" on page 23. 2.7 DMA Mode The DMA Mode (a legacy term) refers to data block transfer operation. The DMA mode affects the state of the RXRDY# and TXRDY# output pins available in the original 16C550. These pins are not available in the XR19L222. The DMA Enable bit (FCR bit-3) does not have any function in this device and can be a '0' or a '1'. 2.8 INT (IRQ#) Output The interrupt output changes according to the operating mode and enhanced features setup. Table 3 and Table 4 below summarize the operating behavior for the transmitter and receiver in the Intel and Motorola modes. Also see Figures 19 through 22. TABLE 3: INT (IRQ#) PIN OPERATION FOR TRANSMITTER
FCR BIT-0 = 0 (FIFO DISABLED) INT Pin (I/M# = 1) IRQ# Pin (I/M# = 0) 0 = one byte in THR 1 = THR empty 1 = one byte in THR 0 = THR empty FCR BIT-0 = 1 (FIFO ENABLED) 0 = FIFO above trigger level 1 = FIFO below trigger level or FIFO empty 1 = FIFO above trigger level 0 = FIFO below trigger level or FIFO empty
TABLE 4: INT (IRQ#) PIN OPERATION FOR RECEIVER
FCR BIT-0 = 0 (FIFO DISABLED) INT Pin (I/M# = 1) IRQ# Pin (I/M# = 0) 0 = no data 1 = 1 byte 1 = no data 0 = 1 byte FCR BIT-0 = 1 (FIFO ENABLED) 0 = FIFO below trigger level 1 = FIFO above trigger level 1 = FIFO below trigger level 0 = FIFO above trigger level
2.9
Crystal or External Clock Input
The L222 includes an on-chip oscillator (XTAL1 and XTAL2) to generate a clock when a crystal is connected between the XTAL1 and XTAL2 pins of the device. Alternatively, an external clock can be supplied through the XTAL1 pin. The CPU data bus does not require this clock for bus operation. The crystal oscillator provides a system clock to the Baud Rate Generators (BRG) section found in each of the UART. XTAL1 is the input to the oscillator or external clock input and XTAL2 pin is the bufferred output which can be used as a clock signal for other devices in the system. Please note that the input XTAL1 is not 5V tolerant and therefore, the maximum
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XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
voltage at the pin should be 3.3V when an external clock is supplied. For programming details, see "Programmable Baud Rate Generator." FIGURE 4. TYPICAL CRYSTAL CONNECTIONS
XTAL1
XTAL2 R1 0-120 (Optional)
R2 500K - 1M Y1 C1 22-47pF C2 22-47pF
1.8432 MHz to 24 MHz
The on-chip oscillator is designed to use an industry standard microprocessor crystal (parallel resonant, fundamental frequency with 10-22 pF capacitance load, ESR of 20-120 ohms and 100ppm frequency tolerance) connected externally between the XTAL1 and XTAL2 pins. When VCC = 5V, the on-chip oscillator can operate with a crystal whose frequency is not greater than 24 MHz. On the other hand, the L222 can accept an external clock of up to 64 MHz at XTAL1 pin also. Although the L222 can accept an external clock of up to 50MHz, the maximum data rate supported by the RS-232 drivers is 1Mbps. For further reading on the oscillator circuit please see the Application Note DAN108 on the EXAR web site at http://www.exar.com. 2.10 Programmable Baud Rate Generator with Fractional Divisor
Each UART has its own Baud Rate Generator (BRG) with a prescaler for the transmitter and receiver. The prescaler is controlled by a software bit in the MCR register. The MCR register bit-7 sets the prescaler to divide the input crystal or external clock by 1 or 4. The output of the prescaler clocks to the BRG. The BRG further divides this clock by a programmable divisor between 1 and (216 - 0.0625) in increments of 0.0625 (1/16) to obtain a 16X or 8X sampling clock of the serial data rate. The sampling clock is used by the transmitter for data bit shifting and receiver for data sampling. The BRG divisor (DLL, DLM and DLD registers) defaults to the value of '1' (DLL = 0x01, DLM = 0x00 and DLD = 0x00) upon reset. Therefore, the BRG must be programmed during initialization to the operating data rate. The DLL and DLM registers provide the integer part of the divisor and the DLD register provides the fractional part of the dvisior. Only the four lower bits of the DLD are implemented and they are used to select a value from 0 (for setting 0000) to 0.9375 or 15/16 (for setting 1111). Programming the Baud Rate Generator Registers DLL, DLM and DLD provides the capability for selecting the operating data rate. Table 5 shows the standard data rates available with a 24MHz crystal or external clock at 16X clock rate. If the pre-scaler is used (MCR bit-7 = 1), the output data rate will be 4 times less than that shown in Table 5. At 8X sampling rate, these data rates would double. Also, when using 8X sampling mode, please note that the bittime will have a jitter (+/- 1/16) whenever the DLD is non-zero and is an odd number. When using a nonstandard data rate crystal or external clock, the divisor value can be calculated with the following equation(s):
Required Divisor (decimal) = (XTAL1 clock frequency / prescaler) / (serial data rate x 16), with 16X mode EMSR[7] = 1 Required Divisor (decimal) = (XTAL1 clock frequency / prescaler / (serial data rate x 8), with 8X mode EMSR[7] = 0
11
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER The closest divisor that is obtainable in the L222 can be calculated using the following formula: ROUND( (Required Divisor - TRUNC(Required Divisor) )*16)/16 + TRUNC(Required Divisor), where
DLM = TRUNC(Required Divisor) >> 8 DLL = TRUNC(Required Divisor) & 0xFF DLD = ROUND( (Required Divisor-TRUNC(Required Divisor) )*16)
REV. 1.0.0
In the formulas above, please note that: TRUNC (N) = Integer Part of N. For example, TRUNC (5.6) = 5. ROUND (N) = N rounded towards the closest integer. For example, ROUND (7.3) = 7 and ROUND (9.9) = 10. A >> B indicates right shifting the value 'A' by 'B' number of bits. For example, 0x78A3 >> 8 = 0x0078. FIGURE 5. BAUD RATE GENERATOR
To Other Channel
DLL, DLM and DLD Registers Prescaler Divide by 1 XTAL1 XTAL2 Crystal Osc/ Buffer Prescaler Divide by 4 MCR Bit-7=0 (default) Fractional Baud Rate Generator Logic MCR Bit-7=1
16X or 8X Sampling Rate Clock to Transmitter and Receiver
12
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
TABLE 5: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING
Required Output Data Rate 400 2400 4800 9600 10000 19200 25000 28800 38400 50000 57600 75000 100000 115200 153600 200000 225000 230400 250000 300000 400000 460800 500000 750000 921600 1000000 DIVISOR FOR 16x Clock (Decimal) 3750 625 312.5 156.25 150 78.125 60 52.0833 39.0625 30 26.0417 20 15 13.0208 9.7656 7.5 6.6667 6.5104 6 5 3.75 3.2552 3 2 1.6276 1.5 DIVISOR OBTAINABLE IN L222 3750 625 312 8/16 156 4/16 150 78 2/16 60 52 1/16 39 1/16 30 26 1/16 20 15 13 9 12/16 7 8/16 6 11/16 6 8/16 6 5 3 12/16 3 4/16 3 2 1 10/16 1 8/16 DLM PROGRAM VALUE (HEX) E 2 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 DLL PROGRAM VALUE (HEX) A6 71 38 9C 96 4E 3C 34 27 1E 1A 14 F D 9 7 6 6 6 5 3 3 3 2 1 1 DLD PROGRAM VALUE (HEX) 0 0 8 4 0 2 0 1 1 0 1 0 0 0 C 8 B 8 0 0 C 4 0 0 A 8 DATA ERROR RATE (%) 0 0 0 0 0 0 0 0.04 0 0 0.08 0 0 0.16 0.16 0 0.31 0.16 0 0 0 0.16 0 0 0.16 0
13
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER FIGURE 6. XR19L222 TRANSMITTER AND RECEIVER
REV. 1.0.0
UART
RS-232 Transceiver
TXA RXA
TXDA RXDA
5K
TXB
TXDB
RXB
RXDB
5K
TXB RXBSEL RXB
2.11
Transmitter
The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 64 bytes of FIFO which includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X/8X internal clock. A bit time is 16 (8) clock periods (see EMSR bit-7). The transmitter sends the start-bit followed by the number of data bits, inserts the proper parity-bit if enabled, and adds the stop-bit(s). The status of the FIFO and TSR are reported in the Line Status Register (LSR bit-5 and bit-6). 2.11.1 Transmit Holding Register (THR) - Write Only The transmit holding register is an 8-bit register providing a data interface to the host processor. The host writes transmit data byte to the THR to be converted into a serial data stream including start-bit, data bits, parity-bit and stop-bit(s). The least-significant-bit (Bit-0) becomes first data bit to go out. The THR is the input register to the transmit FIFO of 64 bytes when FIFO operation is enabled by FCR bit-0. Every time a write operation is made to the THR, the FIFO data pointer is automatically bumped to the next sequential data location. 2.11.2 Transmitter Operation in non-FIFO Mode The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty.
14
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
FIGURE 7. TRANSMITTER OPERATION IN NON-FIFO MODE
Data Byte
Transmit Holding Register (THR)
THR Interrupt (ISR bit-1) Enabled by IER bit-1
16X or 8X Clock (EMSR Bit-7)
Transmit Shift Register (TSR)
M S B
L S B
TXNOFIFO1
2.11.3
Transmitter Operation in FIFO Mode
The host may fill the transmit FIFO with up to 64 bytes of transmit data. The THR empty flag (LSR bit-5) is set whenever the FIFO is empty. The THR empty flag can generate a transmit empty interrupt (ISR bit-1) when the amount of data in the FIFO falls below its programmed trigger level. The transmit empty interrupt is enabled by IER bit-1. The Transmitter Empty Flag (LSR bit-6) is set when both the TSR and the FIFO become empty. FIGURE 8. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE
Transm it D ata B yte
Transm it FIF O
TH R Interrupt (IS R bit-1) falls below the program m ed Trigger Level and then w hen becom es em pty. F IFO is E nabled by FC R bit-0=1
A uto C TS Flow C ontrol (C TS # pin) Flow C ontrol C haracters (X off1/2 and X on1/2 R eg.) A uto S oftw are Flow C ontrol
16X or 8X C lock (E M S R bit-7)
Transm it D ata S hift R egister (TS R )
TX FIFO 1
2.12
RECEIVER
The receiver section contains an 8-bit Receive Shift Register (RSR) and 64 bytes of FIFO which includes a byte-wide Receive Holding Register (RHR). The RSR uses the 16X/8X clock (EMSR bit-7) for timing. It verifies and validates every bit on the incoming character in the middle of each data bit. On the falling edge of a start or false start bit, an internal receiver counter starts counting at the 16X/8X clock rate. After 8 clocks (or 4 if 8X) the start bit period should be at the center of the start bit. At this time the start bit is sampled and if it is still a logic 0 it is validated. Evaluating the start bit in this manner prevents the receiver from assembling a false character. The rest of the data bits and stop bits are sampled and validated in this same manner to prevent false framing. If there were any error(s), they are reported in the LSR register bits 2-4. Upon unloading the receive data byte from RHR, the receive FIFO pointer is bumped and the error tags are immediately updated to reflect the status of the data byte in RHR register. RHR can generate a receive data ready interrupt upon receiving a character or delay until it reaches the FIFO trigger level. Furthermore, data delivery to the host is guaranteed by a receive data ready time-out interrupt when data is not received for 4 word lengths as defined by LCR[1:0] plus 12 bits time. This is equivalent to 3.7-4.6 character times. The RHR interrupt is enabled by IER bit-0.
15
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 2.12.1 Receive Holding Register (RHR) - Read-Only
REV. 1.0.0
The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift Register. It provides the receive data interface to the host processor. The RHR register is part of the receive FIFO of 64 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data byte are immediately updated in the LSR bits 2-4. 2.12.2 Selectable Input to RX of Channel B There is an input (RXBSEL) that selects whether the signal going to the RXB input of the UART will be the signal from the RS-232 transceiver or not. If RXBSEL is LOW, then the signal to the RXB input is the RXDB signal from the RS-232 transceiver. When RXDB is used, the RXB input should be left floating. The signal received at the UART can be probed at the RXB pin. If RXBSEL is HIGH, then the RXDB pin is tri-stated and RXB can be used with an external Infrared transceiver or RS-422 transceiver. If RXB is selected but is unused, RXB should be connected to VCC. See Figure 6 for a detailed drawing. FIGURE 9. RECEIVER OPERATION IN NON-FIFO MODE
16X or 8X Clock (EMSR bit-7)
Receive Data Shift Register (RSR)
Data Bit Validation
Receive Data Characters
Receive Data Byte and Errors
Error Tags in LSR bits 4:2
Receive Data Holding Register (RHR)
RHR Interrupt (ISR bit-2)
RXFIFO1
16
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
FIGURE 10. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE
16X Clock Receive Data Shift Register (RSR) Data Bit Validation
Receive Data Characters
64 bytes by 11-bit wide FIFO
Example: - RX FIFO trigger level selected at 16 bytes (See Note below) Data falls to 8 Error Tags (64-sets)
Receive Data FIFO
RTS# re-asserts when data falls below the flow control trigger level to restart remote transmitter. Enable by EFR bit-6=1, MCR bit-1. RHR Interrupt (ISR bit-2) programmed for desired FIFO trigger level. FIFO is Enabled by FCR bit-0=1 control trigger level to suspend remote transmitter. Enable by EFR bit-6=1, MCR bit-1.
FIFO Trigger=16
Data fills to 24 RTS# de-asserts when data fills above the flow Error Tags in LSR bits 4:2
Receive Data Byte and Errors
Receive Data
RXFIFO1
NOTE: Table-B selected as Trigger Table for Figure 10 (Table 14).
2.13
Auto RTS (Hardware) Flow Control
Automatic RTS hardware flow control is used to prevent data overrun to the local receiver FIFO. The RTS output is used to request remote unit to suspend/resume data transmission. The auto RTS flow control feature is enabled to fit specific application requirement (see Figure 11):
* Enable auto RTS flow control using EFR bit-6. * The auto RTS function must be started by asserting RTS output pin (MCR bit-1 to logic 1 after it is enabled).
If using the Auto RTS interrupt:
* Enable RTS interrupt through IER bit-6 (after setting EFR bit-4). The UART issues an interrupt when the RTS
pin makes a transition from low to high: ISR bit-5 will be set to logic 1. 2.14 Auto RTS Hysteresis The L222 has a new feature that provides flow control trigger hysteresis while maintaining compatibility with the XR16C850, ST16C650A and ST16C550 family of UARTs. With the Auto RTS function enabled, an interrupt is generated when the receive FIFO reaches the programmed RX trigger level. The RTS pin will not be deasserted until the receive FIFO reaches the upper limit of the hysteresis level. The RTS pin will be re-asserted after the RX FIFO is unloaded to the lower limit of the hysteresis level. Under the above described conditions, the L222 will continue to accept data until the receive FIFO gets full. The Auto RTS function is initiated when the RTS output pin is asserted. Table 13 shows the complete details for the Auto RTS Hysteresis levels. Please note that this table is for programmable trigger levels only (Table D). The hysteresis values for Tables A-C are the next higher and next lower trigger levels in the corresponding table.
17
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 2.15 Auto CTS Flow Control
REV. 1.0.0
Automatic CTS flow control is used to prevent data overrun to the remote receiver FIFO. The CTS input is monitored to suspend/restart the local transmitter. The auto CTS flow control feature is selected to fit specific application requirement (see Figure 11):
* Enable auto CTS flow control using EFR bit-7.
If using the Auto CTS interrupt:
* Enable CTS interrupt through IER bit-7 (after setting EFR bit-4). The UART issues an interrupt when the CTS
pin is de-asserted: ISR bit-5 will be set to 1, and UART will suspend transmission as soon as the stop bit of the character in process is shifted out. Transmission is resumed after the CTS input is re-asserted, indicating more data may be sent. FIGURE 11. AUTO RTS AND CTS FLOW CONTROL OPERATION
The signals shown in this figure are the signals at the UART and not at the RS-232 transceiver.
Local UART UARTA Receiver FIFO Trigger Reached Auto RTS Trigger Level Transmitter Auto CTS Monitor RXA TXB Remote UART UARTB Transmitter Auto CTS Monitor Receiver FIFO Trigger Reached Auto RTS Trigger Level
RTSA# TXA
CTSB# RXB
CTSA# Assert RTS# to Begin Transmission 1 ON 2 7 ON 3 8 OFF
RTSB#
RTSA# CTSB# TXB
OFF
10 11
ON ON
Data Starts 4 RXA FIFO INTA (RXA FIFO Interrupt) Receive RX FIFO Data Trigger Level 5
6
Suspend
Restart 9
RTS High Threshold
RTS Low Threshold
12
RX FIFO Trigger Level
RTSCTS1
The local UART (UARTA) starts data transfer by asserting RTSA# (1). RTSA# is normally connected to CTSB# (2) of remote UART (UARTB). CTSB# allows its transmitter to send data (3). TXB data arrives and fills UARTA receive FIFO (4). When RXA data fills up to its receive FIFO trigger level, UARTA activates its RXA data ready interrupt (5) and continues to receive and put data into its FIFO. If interrupt service latency is long and data is not being unloaded, UARTA monitors its receive data fill level to match the upper threshold of RTS delay and de-assert RTSA# (6). CTSB# follows (7) and request UARTB transmitter to suspend data transfer. UARTB stops or finishes sending the data bits in its transmit shift register (8). When receive FIFO data in UARTA is unloaded to match the lower threshold of RTS delay (9), UARTA re-asserts RTSA# (10), CTSB# recognizes the change (11) and restarts its transmitter and data flow again until next receive FIFO trigger (12). This same event applies to the reverse direction when UARTA sends data to UARTB with RTSB# and CTSA# controlling the data flow.
18
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER Auto Xon/Xoff (Software) Flow Control
2.16
When software flow control is enabled (See Table 15), the L222 compares one or two sequential receive data characters with the programmed Xon or Xoff-1,2 character value(s). If receive character(s) (RX) match the programmed values, the L222 will halt transmission (TX) as soon as the current character has completed transmission. When a match occurs, the Xoff (if enabled via IER bit-5) flag will be set and the interrupt output pin will be activated. Following a suspension due to a match of the Xoff character, the L222 will monitor the receive data stream for a match to the Xon-1,2 character. If a match is found, the L222 will resume operation and clear the flags (ISR bit-4). Reset initially sets the contents of the Xon/Xoff 8-bit flow control registers to a logic 0. Following reset the user can write any Xon/Xoff value desired for software flow control. Different conditions can be set to detect Xon/ Xoff characters (See Table 15) and suspend/resume transmissions. When double 8-bit Xon/Xoff characters are selected, the L222 compares two consecutive receive characters with two software flow control 8-bit values (Xon1, Xon2, Xoff1, Xoff2) and controls TX transmissions accordingly. Under the above described flow control mechanisms, flow control characters are not placed (stacked) in the user accessible RX data buffer or FIFO. In the event that the receive buffer is overfilling and flow control needs to be executed, the L222 automatically sends an Xoff message (when enabled) via the serial TX output to the remote modem. The L222 sends the Xoff-1,2 characters two-character-times (= time taken to send two characters at the programmed baud rate) after the receive FIFO crosses the programmed trigger level (for all trigger tables A-D). To clear this condition, the L222 will transmit the programmed Xon-1,2 characters as soon as receive FIFO is less than one trigger level below the programmed trigger level (for Trigger Tables A, B, and C) or when receive FIFO is less than the trigger level minus the hysteresis value (for Trigger Table D). This hysteresis value is the same as the Auto RTS Hysteresis value in Table 13. Table 6 below explains this when Trigger Table-B (See Table 14) is selected. TABLE 6: AUTO XON/XOFF (SOFTWARE) FLOW CONTROL
RX TRIGGER LEVEL 8 16 24 28 INT PIN ACTIVATION 8 16 24 28 XOFF CHARACTER(S) SENT (CHARACTERS IN RX FIFO) 8* 16* 24* 28* XON CHARACTER(S) SENT (CHARACTERS IN RX FIFO) 0 8 16 24
* After the trigger level is reached, an xoff character is sent after a short span of time (= time required to send 2 characters);
for example, after 2.083ms has elapsed for 9600 baud and 8-bit word length, no parity and 1 stop bit setting.
2.17
Special Character Detect
A special character detect feature is provided to detect an 8-bit character when bit-5 is set in the Enhanced Feature Register (EFR). When this character (Xoff2) is detected, it will be placed in the FIFO along with normal incoming RX data. The L222 compares each incoming receive character with the programmed Xoff-2 data. If a match exists, the received data will be transferred to the RX FIFO and ISR bit-4 will be set to indicate detection of special character. Although the Internal Register Table shows Xon, Xoff Registers with eight bits of character information, the actual number of bits is dependent on the programmed word length. Line Control Register (LCR) bits 0-1 define the number of character bits, i.e., either 5 bits, 6 bits, 7 bits, or 8 bits. The word length selected by LCR bits 0-1 also determines the number of bits that will be used for the special character comparison. Bit-0 in the Xon, Xoff Registers corresponds with the LSB bit for the receive character.
19
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 2.18 Sleep Modes and Power-Save Feature with Wake-Up Interrupt
REV. 1.0.0
There are three levels of power management integrated in the L222. The device is low power with low operational and standby supply currents. In the Partial Sleep mode, the internal oscillator of the UART or charge pump of the RS-232 transceiver is turned off to reduce the power consumption. In the Full Sleep mode, both the oscillator and the charge pump are turned off. The Power-save mode provides additional power saving by isolating the UART address, data and control signals during Sleep mode to minimize the power consumption. 2.18.1 Partial Sleep Mode There are two different partial sleep modes. In the first mode, the UART is in sleep mode and the charge pump is active. In the other mode, the UART is still active but the charge pump is turned off. 2.18.1.1 UART in sleep mode, RS-232 transceiver active If the ACP pin is LOW, then the charge pump for the RS-232 transceiver will always be active. But the UART portion in the L222 can still enter sleep mode if all of these conditions are satisfied:

no interrupts pending (ISR bit-0 = 1) the 16-bit divisor programmed in DLM and DLL registers is a non-zero value sleep mode is enabled (IER bit-4 = 1) modem inputs are not toggling (MSR bits 0-3 = 0) RXD input pin is idling LOW
The L222 stops its crystal oscillator to conserve power in this mode. The user can check the XTAL2 pin for no clock output as an indication that the device has entered the partial sleep mode. The UART portion in the L222 resumes normal operation or active mode by any of the following:

a receive data start bit transition on the RXD input (LOW to HIGH) a data byte is loaded to the transmitter, THR or FIFO a change of logic state on any of the modem or general purpose serial inputs: i.e., any of the MSR bits 03 shows a '1'
If the sleep mode is enabled and the L222 is awakened by one of the conditions described above, an interrupt is issued by the L222 to signal to the CPU that it is awake. The lower nibble of the interrupt source register (ISR) will read a value of 0x1 for this interrupt and reading the ISR clears this interrupt. Since the same value (0x1) is also used to indicate no pending interrupt, users should exercise caution while using the sleep mode. The UART portion in the L222 will return to the sleep mode automatically after all interrupting conditions have been serviced and cleared. If the UART portion of the L222 is awakened by the modem inputs, a read to the MSR is required to reset the modem inputs. In any case, the sleep mode will not be entered while an interrupt is pending. The UART portion of the L222 will stay in the sleep mode of operation until it is disabled by setting IER bit-4 to a logic 0.
20
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER UART active, charge pump of RS-232 transceiver shut down
2.18.1.2
If the ACP pin is HIGH and the UART portion of the L222 is not in sleep mode, then the charge pump will automatically shut down to conserve power if the following conditions are true:

no activity on the TXD output signal modem input signals (RX, CTS, DSR, CD, RI) are LOW modem inputs have been idle for approximately 30 seconds
When these conditions are satisfied, the L222 shuts down the charge pump and tri-states the RS-232 drivers to conserve power. In this mode, the RS-232 receivers are fully active and the internal registers of the L222 can be accessed. The time for the charge pump to resume normal operation after exiting the sleep mode is typically 45s. It will wake up by any of the following:

a receive data start bit transition on the RXD input (LOW to HIGH) a data byte is loaded to the transmitter, THR or FIFO a LOW to HIGH transition on any of the modem or general purpose serial inputs
Because the receivers are fully active when the charge pump is turned off, any data received will be transferred to/from the UART without any issues. 2.18.2 Full Sleep Mode In full sleep mode, the L222 shuts down the charge pump and the internal oscillator. The L222 enters the full sleep mode if the following conditions are satisfied:

the UART portion of the L222 is already in sleep mode (no output on XTAL2) the ACP (Autosleep for Charge Pump) pin is HIGH
When these conditions are satisfied, both the UART and the charge pump will be in the sleep mode. In this mode, the RS-232 receivers are fully active and the internal registers of the L222 can be accessed. The L222 exits the full sleep mode if either the ACP pin becomes LOW or the internal oscillator starts up. The time for the charge pump to resume normal operation after exiting the full sleep mode is typically 45s. 2.18.3 Power-Save Feature This mode is in addition to the sleep mode and in this mode, the core logic of the L222 is isolated from the CPU interface. If the address lines, data bus lines, IOW#, IOR# and CS# remain steady when the L222 is in full sleep mode, the maximum current will be in the microamp range as specified in the DC Electrical Characteristics on page 42. However, if the input lines are floating or are toggling while the L222 is in sleep mode, the current can be up to 100 times more. If not using the Power-Save feature, an external buffer would be required to keep the address and data bus lines from toggling or floating to achieve the low current. But if the Power-Save feature is enabled (PwrSave pin connected to VCC), this will eliminate the need for an external buffer by internally isolating the address, data and control signals from other bus activities that could cause wasteful power drain (see Figure 1). The L222 enters Power-Save mode when this pin is connected to VCC, and the UART portion of the L222 is already in sleep mode. Since Power-Save mode isolates the address, data and control signals, the device will wake-up only by:

a receive data start bit transition, or a change of logic state on any of the modem or general purpose serial inputs: i.e., any of the MSR bits 03 shows a '1'
The L222 will return to the Power-Save mode automatically after a read to the MSR (to reset the modem inputs) and all interrupting conditions have been serviced and cleared. The L222 will stay in the Power-Save mode of operation until it is disabled by setting IER bit-4 to a logic 0 and/or the Power-Save pin is connected to GND. If the L222 is awakened by any one of the above conditions, it issues an interrupt as soon as the oscillator circuit is up and running and the device is ready to transmit/receive. This interrupt has the same encoding (bit0 of ISR register = 1) as "no interrupt pending" and will clear when the ISR register is read. This will show up in the ISR register only if no other interrupts are enabled.
21
XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 2.19 Infrared Mode (UART Channel B Only)
REV. 1.0.0
The L222 includes an infrared encoder and decoder compatible to the IrDA (Infrared Data Association) version 1.0. The IrDA 1.0 standard that stipulates the infrared encoder sends out a 3/16 of a bit wide HIGH-pulse for each "0" bit in the transmit data stream. This signal encoding reduces the on-time of the infrared LED, hence reduces the power consumption. See Figure 12 below. The infrared encoder and decoder are enabled by setting MCR register bit-6 to a `1'. When the infrared feature is enabled, the transmit data output, TXB, idles at logic zero level. Likewise, the RX input assumes an idle level of logic zero from a reset and power up, see Figure 12. Typically, the wireless infrared decoder receives the input pulse from the infrared sensing diode on the RXB pin. Each time it senses a light pulse, it returns a HIGH to the data bit stream. However, this is not true with some infrared modules on the market which indicate a LOW by a light pulse. So the L222 has a provision to invert the input polarity to accommodate this. In this case user can enable FCTR bit-2 to invert the input signal. The Infrared Mode can only be used with channel B of the L222 using the TXB output and the RXB input pins.. FIGURE 12. INTERNAL LOOP BACK
VCC Transmit Shift Register (THR/FIFO) MCR bit-4=1 Internal Data Bus Lines and Control Signals Receive Shift Register (RHR/FIFO) VCC RTS Modem / General Purpose Control Logic TXA/ TXB
RXA/ RXB RTSA#/ RTSB#
CTS VCC DTR
CTSA#/ CTSB# DTRA#/ DTRB#
DSR OP1# RI OP2# CD
DSRA#/ DSRB# RIA#/ RIB# CDA#/ CDB#
22
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
3.0 UART INTERNAL REGISTERS The L222 has a set of configuration registers selected by address lines A0, A1 and A2 with CS# asserted. The complete register set is shown on Table 7 and Table 8. TABLE 7: UART INTERNAL REGISTERS
ADDRESSES A2 A1 A0 REGISTER 16C550 COMPATIBLE REGISTERS 0 00 RHR - Receive Holding Register THR - Transmit Holding Register DLL - Divisor LSB DLM - Divisor MSB DLD - Divisor Fractional DREV - Device Revision Code DVID - Device Identification Code IER - Interrupt Enable Register ISR - Interrupt Status Register FCR - FIFO Control Register LCR - Line Control Register MCR - Modem Control Register LSR - Line Status Register MSR - Modem Status Register SPR - Scratch Pad Register FLVL - RX/TX FIFO Level Counter Register EMSR - Enhanced Mode Select Register ENHANCED REGISTERS 0 00 TRG - RX/TX FIFO Trigger Level Register FC - RX/TX FIFO Level Counter Register FCTR - Feature Control Register EFR - Enhanced Function Register Xon-1 - Xon Character 1 Xon-2 - Xon Character 2 Xoff-1 - Xoff Character 1 Xoff-2 - Xoff Character 2 Write-only Read-only Read/Write Read/Write Read/Write Read/Write Read/Write Read/Write LCR = 0xBF Read-only Write-only Read/Write Read/Write Read/Write Read-only Read-only Read/Write Read-only Write-only Read/Write Read/Write Read-only Read-only Read/Write Read-only Write-only LCR 0xBF, FCTR[6] = 0 LCR 0xBF, FCTR[6] = 1 LCR 0xBF LCR[7] = 1, LCR 0xBF, EFR[4] = 1 DLL, DLM = 0x00, LCR[7] = 1, LCR 0xBF LCR[7] = 0 LCR 0xBF LCR[7] = 0 READ/WRITE COMMENTS
0 0 0 0 0 0 0
00 01 10 00 01 01 10
LCR[7] = 1, LCR 0xBF
0 1 1 1 1 1 1
11 00 01 10 11 11 11
0 0 1 1 1 1
01 10 00 01 10 11
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TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1
ADDRESS A2-A0 REG NAME READ/ WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT
16C550 Compatible Registers 000 000 001 RHR THR IER RD WR RD/WR Bit-7 Bit-7 0/ Bit-6 Bit-6 0/ Bit-5 Bit-5 0/ Xoff Int. Enable Bit-4 Bit-4 0/ Sleep Mode Enable Bit-3 Bit-3 Bit-2 Bit-2 Bit-1 Bit-1 Bit-0 Bit-0 LCR[7]=0
CTS Int. RTS Int. Enable Enable
Modem RX Line TX RX Stat. Int. Stat. Empty Data Enable Int. Int Int. Enable Enable Enable
010
ISR
RD
FIFOs FIFOs Enabled Enabled
0/ INT Source Bit-5 0/
0/ INT Source Bit-4 0/
INT Source Bit-3
INT INT INT Source Source Source Bit-2 Bit-1 Bit-0 LCR 0xBF
010
FCR
WR
RX FIFO RX FIFO Trigger Trigger
TX FIFO TX FIFO Trigger Trigger
DMA Mode Enable
TX FIFO Reset
RX FIFO Reset
FIFOs Enable
011
LCR
RD/WR
Divisor Enable
Set TX Break
Set Parity
Even Parity
Parity Enable
Stop Bits
Word Word Length Length Bit-1 Bit-0
100
MCR
RD/WR
0/ BRG Prescaler
Internal OP2#/INT Rsrvd RTS# DTR# Lopback Output (OP1#) Output Output IR Mode XonAny Enable Enable Control Control ENable
0/
0/
101
LSR
RD
RX FIFO Global Error CD# Input Bit-7
THR & TSR Empty RI# Input Bit-6
THR Empty
RX Break
RX Framing Error
RX Parity Error Delta RI# Bit-2
RX Overrun Error Delta DSR# Bit-1
RX Data Ready Delta CTS# Bit-0
LCR 0xBF
110 111
MSR SPR
RD RD/WR
DSR# Input Bit-5
CTS# Input Bit-4
Delta CD# Bit-3
LCR 0xBF FCTR[6]=0
111
EMSR
WR
16X Sampling Rate Mode
LSR Error Interrupt. Imd/Dly#
Auto RTS Hyst. bit-3
Auto RTS Hyst. bit-2
Rsrvd
Rsrvd
Rx/Tx FIFO Count
Rx/Tx FIFO Count LCR 0xBF FCTR[6]=1
111
FLVL
RD
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
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TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1
ADDRESS A2-A0 REG NAME READ/ WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT
Baud Rate Generator Divisor 000 001 010 DLL DLM DLD RD/WR RD/WR RD/WR Bit-7 Bit-7 0 Bit-6 Bit-6 0 Bit-5 Bit-5 0 Bit-4 Bit-4 0 Bit-3 Bit-3 Bit-3 Bit-2 Bit-2 Bit-2 Bit-1 Bit-1 Bit-1 Bit-0 Bit-0 Bit-0 LCR[7]=1 LCR 0xBF LCR[7]=1 LCR 0xBF EFR[4] = 1 LCR[7]=1 LCR 0xBF DLL=0x00 DLM=0x00
000 001
DREV DVID
RD RD
Bit-7 0
Bit-6 0
Bit-5 0
Bit-4 0
Bit-3 1
Bit-2 0
Bit-1 1
Bit-0 0
Enhanced Registers 000 000 001 TRG FC WR RD Bit-7 Bit-7 RX/TX Mode Bit-6 Bit-6 SCPAD Swap Bit-5 Bit-5 Trig Table Bit-1 Special Char Select Bit-4 Bit-4 Trig Table Bit-0
Enable IER [7:4], ISR [5:4], FCR[5:4], MCR[7:5], DLD
Bit-3 Bit-3 Rsrvd
Bit-2 Bit-2 RX IR Input Inv. Software Flow Cntl Bit-2 Bit-2 Bit-2 Bit-2 Bit-2
Bit-1 Bit-1 Auto RTS Hyst Bit-1 Software Flow Cntl Bit-1 Bit-1 Bit-1 Bit-1 Bit-1
Bit-0 Bit-0 Auto RTS Hyst Bit-0 Software Flow Cntl Bit-0 Bit-0 Bit-0 Bit-0 Bit-0
FCTR RD/WR
010
EFR
RD/WR
Auto CTS Enable
Auto RTS Enable
Software Flow Cntl Bit-3 Bit-3 Bit-3 Bit-3 Bit-3
LCR=0XBF
100 101 110 111
XON1 RD/WR XON2 RD/WR XOFF1 RD/WR XOFF2 RD/WR
Bit-7 Bit-7 Bit-7 Bit-7
Bit-6 Bit-6 Bit-6 Bit-6
Bit-5 Bit-5 Bit-5 Bit-5
Bit-4 Bit-4 Bit-4 Bit-4
4.0 INTERNAL REGISTER DESCRIPTIONS 4.1 4.2 4.3 Receive Holding Register (RHR) - Read- Only Transmit Holding Register (THR) - Write-Only Interrupt Enable Register (IER) - Read/Write SEE "RECEIVER" ON PAGE 15. SEE "TRANSMITTER" ON PAGE 14.
The Interrupt Enable Register (IER) masks the interrupts from receive data ready, transmit empty, line status and modem status registers. These interrupts are reported in the Interrupt Status Register (ISR).
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 4.3.1 IER versus Receive FIFO Interrupt Mode Operation
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When the receive FIFO (FCR BIT-0 = 1) and receive interrupts (IER BIT-0 = 1) are enabled, the RHR interrupts (see ISR bits 2 and 3) status will reflect the following: A. The receive data available interrupts are issued to the host when the FIFO has reached the programmed trigger level. It will be cleared when the FIFO drops below the programmed trigger level. B. FIFO level will be reflected in the ISR register when the FIFO trigger level is reached. Both the ISR register status bit and the interrupt will be cleared when the FIFO drops below the trigger level. C. The receive data ready bit (LSR BIT-0) is set as soon as a character is transferred from the shift register to the receive FIFO. It is reset when the FIFO is empty. 4.3.2 IER versus Receive/Transmit FIFO Polled Mode Operation
When FCR BIT-0 equals a logic 1 for FIFO enable; resetting IER bits 0-3 enables the XR16V2751 in the FIFO polled mode of operation. Since the receiver and transmitter have separate bits in the LSR either or both can be used in the polled mode by selecting respective transmit or receive control bit(s). A. LSR BIT-0 indicates there is data in RHR or RX FIFO. B. LSR BIT-1 indicates an overrun error has occurred and that data in the FIFO may not be valid. C. LSR BIT 2-4 provides the type of receive data errors encountered for the data byte in RHR, if any. D. LSR BIT-5 indicates THR is empty. E. LSR BIT-6 indicates when both the transmit FIFO and TSR are empty. F. LSR BIT-7 indicates a data error in at least one character in the RX FIFO. IER[0]: RHR Interrupt Enable The receive data ready interrupt will be issued when RHR has a data character in the non-FIFO mode or when the receive FIFO has reached the programmed trigger level in the FIFO mode.
* Logic 0 = Disable the receive data ready interrupt (default). * Logic 1 = Enable the receiver data ready interrupt.
IER[1]: THR Interrupt Enable This bit enables the Transmit Ready interrupt which is issued whenever the THR becomes empty in the nonFIFO mode or when data in the FIFO falls below the programmed trigger level in the FIFO mode. If the THR is empty when this bit is enabled, an interrupt will be generated.
* Logic 0 = Disable Transmit Ready interrupt (default). * Logic 1 = Enable Transmit Ready interrupt.
IER[2]: Receive Line Status Interrupt Enable If any of the LSR register bits 1, 2, 3 or 4 is a logic 1, it will generate an interrupt to inform the host controller about the error status of the current data byte in FIFO. LSR bit-1 generates an interrupt immediately when the character has been received. LSR bits 2-4 generate an interrupt when the character with errors is read out of the FIFO (default). Instead, LSR bits 2-4 can be programmed to generate an interrupt immediately, by setting EMSR bit-6 to a logic 1.
* Logic 0 = Disable the receiver line status interrupt (default). * Logic 1 = Enable the receiver line status interrupt.
IER[3]: Modem Status Interrupt Enable
* Logic 0 = Disable the modem status register interrupt (default). * Logic 1 = Enable the modem status register interrupt.
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IER[4]: Sleep Mode Enable (requires EFR bit-4 = 1)
* Logic 0 = Disable Sleep Mode (default). * Logic 1 = Enable Sleep Mode. See Sleep Mode section for further details.
IER[5]: Xoff Interrupt Enable (requires EFR bit-4=1)
* Logic 0 = Disable the software flow control, receive Xoff interrupt (default). * Logic 1 = Enable the software flow control, receive Xoff interrupt. See Software Flow Control section for
details. IER[6]: RTS# Output Interrupt Enable (requires EFR bit-4=1)
* Logic 0 = Disable the RTS# interrupt (default). * Logic 1 = Enable the RTS# interrupt. The UART issues an interrupt when the RTS# pin makes a transition
from low to high. IER[7]: CTS# Input Interrupt Enable (requires EFR bit-4=1)
* Logic 0 = Disable the CTS# interrupt (default). * Logic 1 = Enable the CTS# interrupt. The UART issues an interrupt when CTS# pin makes a transition from
low to high. 4.4 Interrupt Status Register (ISR) - Read-Only
The UART provides multiple levels of prioritized interrupts to minimize external software interaction. The Interrupt Status Register (ISR) provides the user with six interrupt status bits. Performing a read cycle on the ISR will give the user the current highest pending interrupt level to be serviced, others are queued up to be serviced next. No other interrupts are acknowledged until the pending interrupt is serviced. The Interrupt Source Table, Table 9, shows the data values (bit 0-5) for the interrupt priority levels and the interrupt sources associated with each of these interrupt levels. 4.4.1 Interrupt Generation:
* LSR is by any of the LSR bits 1, 2, 3 and 4. * RXRDY is by RX trigger level. * RXRDY Time-out is by a 4-char plus 12 bits delay timer. * TXRDY is by TX trigger level or TX FIFO empty (or transmitter empty in auto RS-485 control). * MSR is by any of the MSR bits 0, 1, 2 and 3. * Receive Xoff/Special character is by detection of a Xoff or Special character. * CTS# is when its transmitter toggles the input pin (from LOW to HIGH) during auto CTS flow control. * RTS# is when its receiver toggles the output pin (from LOW to HIGH) during auto RTS flow control. * Wake-up Indicator is when the UART comes out of sleep mode.
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 4.4.2 Interrupt Clearing:
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* LSR interrupt is cleared by a read to the LSR register. * RXRDY interrupt is cleared by reading data until FIFO falls below the trigger level. * RXRDY Time-out interrupt is cleared by reading RHR. * TXRDY interrupt is cleared by a read to the ISR register or writing to THR. * MSR interrupt is cleared by a read to the MSR register. * Xoff interrupt is cleared by a read to ISR or when Xon character(s) is received. * Special character interrupt is cleared by a read to ISR or after the next character is received. * RTS# and CTS# flow control interrupts are cleared by a read to the MSR register. * Wake-up Indicator is cleared by a read to the ISR register.
]
TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL
PRIORITY LEVEL 1 2 3 4 5 6 7 BIT-5 0 0 0 0 0 0 1 0 ISR REGISTER STATUS BITS BIT-4 0 0 0 0 0 1 0 0 BIT-3 0 1 0 0 0 0 0 0 BIT-2 1 1 1 0 0 0 0 0 BIT-1 1 0 0 1 0 0 0 0 BIT-0 0 0 0 0 0 0 0 1 LSR (Receiver Line Status Register) RXRDY (Receive Data Time-out) RXRDY (Received Data Ready) TXRDY (Transmit Ready) MSR (Modem Status Register) RXRDY (Received Xoff or Special character) CTS#, RTS# change of state None (default) or Wake-up Indicator SOURCE OF INTERRUPT
ISR[0]: Interrupt Status
* Logic 0 = An interrupt is pending and the ISR contents may be used as a pointer to the appropriate interrupt
service routine.
* Logic 1 = No interrupt pending (default condition) or the device has come out of sleep mode.
ISR[3:1]: Interrupt Status These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source Table 9). ISR[4]: Xoff or Special Character Interrupt Status (requires EFR bit-4=1) This bit is enabled when IER[5] = 1. ISR bit-4 indicates that the receiver detected a data match of the Xoff character(s) or special character (XOFF2). ISR[5]: RTS#/CTS# Interrupt Status (requires EFR bit-4=1) This bit is enabled when IER[7] = 1 or IER[6] = 1. ISR bit-5 indicates that the CTS# or RTS# has been deasserted. ISR[7:6]: FIFO Enable Status These bits are set to a logic 0 when the FIFOs are disabled. They are set to a logic 1 when the FIFOs are enabled. 4.5 FIFO Control Register (FCR) - Write-Only
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This register is used to enable the FIFOs, clear the FIFOs, set the transmit/receive FIFO trigger levels, and select the DMA mode. The DMA, and FIFO modes are defined as follows: FCR[0]: TX and RX FIFO Enable
* Logic 0 = Disable the transmit and receive FIFO (default). * Logic 1 = Enable the transmit and receive FIFOs. This bit must be set to logic 1 when other FCR bits are
written or they will not be programmed. FCR[1]: RX FIFO Reset This bit is only active when FCR bit-0 is a `1'.
* Logic 0 = No receive FIFO reset (default) * Logic 1 = Reset the receive FIFO pointers and FIFO level counter logic (the receive shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO. FCR[2]: TX FIFO Reset This bit is only active when FCR bit-0 is a `1'.
* Logic 0 = No transmit FIFO reset (default). * Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not
cleared or altered). This bit will return to a logic 0 after resetting the FIFO. FCR[3]: DMA Mode Select Controls the behavior of the TXRDY# and RXRDY# pins. See DMA operation section for details.
* Logic 0 = Normal Operation (default). * Logic 1 = DMA Mode.
FCR[5:4]: Transmit FIFO Trigger Select (requires EFR bit-4=1) (logic 0 = default, TX trigger level = 1) These 2 bits set the trigger level for the transmit FIFO. The UART will issue a transmit interrupt when the number of characters in the FIFO falls below the selected trigger level, or when it gets empty in case that the FIFO did not get filled over the trigger level on last re-load. Table 10 below shows the selections. EFR bit-4 must be set to `1' before these bits can be accessed. Note that the receiver and the transmitter cannot use different trigger tables. Whichever selection is made last applies to both the RX and TX side. FCR[7:6]: Receive FIFO Trigger Select (logic 0 = default, RX trigger level =1) The FCTR Bits 5-4 are associated with these 2 bits. These 2 bits are used to set the trigger level for the receive FIFO. The UART will issue a receive interrupt when the number of the characters in the FIFO crosses the trigger level. Table 10 shows the complete selections. Note that the receiver and the transmitter cannot use different trigger tables. Whichever selection is made last applies to both the RX and TX side.
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION
TRIGGER TABLE Table-A FCTR BIT-5 0 FCTR BIT-4 0 0 0 1 1 Table-B 0 1 0 1 0 1 0 0 1 1 0 0 1 1 Table-C 1 0 0 1 0 1 0 0 1 1 0 0 1 1 Table-D 1 1 X 0 1 0 1 X X X 0 1 0 1 8 16 56 60 Programmable Programmable 16L2752, 16C2850, 16C2852, 16C850, via TRG via TRG 16C854, 16C864 register. register. FCTR[7] = 0. FCTR[7] = 1. 0 1 0 1 8 16 24 28 8 16 32 56 16C654 FCR BIT-7 FCR BIT-6 FCR BIT-5 0 FCR
BIT-4
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RECEIVE TRIGGER LEVEL
TRANSMIT TRIGGER LEVEL 1 (default)
COMPATIBILITY 16C550, 16C2550, 16C2552, 16C554, 16C580
0 1 (default) 4 8 14
16 8 24 30
16C650A
4.6
Line Control Register (LCR) - Read/Write
The Line Control Register is used to specify the asynchronous data communication format. The word or character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this register. LCR[1:0]: TX and RX Word Length Select These two bits specify the word length to be transmitted or received.
BIT-1 0 0 1 1
BIT-0 0 1 0 1
WORD LENGTH 5 (default) 6 7 8
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LCR[2]: TX and RX Stop-bit Length Select The length of stop bit is specified by this bit in conjunction with the programmed word length.
BIT-2 0 1 1
WORD
LENGTH
STOP BIT LENGTH (BIT TIME(S)) 1 (default) 1-1/2 2
5,6,7,8 5 6,7,8
LCR[3]: TX and RX Parity Select Parity or no parity can be selected via this bit. The parity bit is a simple way used in communications for data integrity check. See Table 11 for parity selection summary below.
* Logic 0 = No parity. * Logic 1 = A parity bit is generated during the transmission while the receiver checks for parity error of the
data character received. LCR[4]: TX and RX Parity Select If the parity bit is enabled with LCR bit-3 set to a logic 1, LCR bit-4 selects the even or odd parity format.
* Logic 0 = ODD Parity is generated by forcing an odd number of logic 1's in the transmitted character. The
receiver must be programmed to check the same format (default).
* Logic 1 = EVEN Parity is generated by forcing an even number of logic 1's in the transmitted character. The
receiver must be programmed to check the same format. LCR[5]: TX and RX Parity Select If the parity bit is enabled, LCR BIT-5 selects the forced parity format.
* LCR BIT-5 = logic 0, parity is not forced (default). * LCR BIT-5 = logic 1 and LCR BIT-4 = logic 0, parity bit is forced to a logical 1 for the transmit and receive
data.
* LCR BIT-5 = logic 1 and LCR BIT-4 = logic 1, parity bit is forced to a logical 0 for the transmit and receive
data. TABLE 11: PARITY SELECTION
LCR BIT-5 LCR BIT-4 LCR BIT-3 X 0 0 1 1 X 0 1 0 1 0 1 1 1 1 PARITY SELECTION No parity Odd parity Even parity Force parity to mark, "1" Forced parity to space, "0"
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER LCR[6]: Transmit Break Enable When enabled, the Break control bit causes a break condition to be transmitted (the TX output is forced to a "space", LOW state). This condition remains, until disabled by setting LCR bit-6 to a logic 0.
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* Logic 0 = No TX break condition (default). * Logic 1 = Forces the transmitter output (TX) to a "space", LOW, for alerting the remote receiver of a line
break condition. LCR[7]: Baud Rate Divisors Enable Baud rate generator divisor (DLL, DLM and DLD) enable.
* Logic 0 = Data registers are selected (default). * Logic 1 = Divisor latch registers are selected.
4.7 Modem Control Register (MCR) or General Purpose Outputs Control - Read/Write The MCR register is used for controlling the serial/modem interface signals or general purpose inputs/outputs. MCR[0]: DTR# Output The DTR# pin is a modem control output. If the modem interface is not used, this output may be used as a general purpose output.
* Logic 0 = Force DTR# output HIGH (default). * Logic 1 = Force DTR# output LOW.
MCR[1]: RTS# Output The RTS# pin is a modem control output and may be used for automatic hardware flow control by enabled by EFR bit-6. The RTS# pin can also be used for Auto RS485 Half-Duplex direction control enabled by FCTR bit3. If the modem interface is not used, this output may be used as a general purpose output.
* Logic 0 = Force RTS# HIGH (default). * Logic 1 = Force RTS# LOW.
MCR[2]: Reserved OP1# is not available as an output pin on the L222. But it is available for use during Internal Loopback Mode. In the Loopback Mode, this bit is used to write the state of the modem RI# interface signal. MCR[3]: OP2# Output / INT Output Enable This bit enables or disables the operation of INT, interrupt output. If INT output is not used, OP2# can be used as a general purpose output. Also, if 16/68# pin selects Motorola bus interface mode, this bit must be set to logic 0.
* Logic 0 = INT (A-B) outputs disabled (three state mode) and OP2# output set HIGH(default). * Logic 1 = INT (A-B) outputs enabled (active mode) and OP2# output set LOW.
MCR[4]: Internal Loopback Enable
* Logic 0 = Disable loopback mode (default). * Logic 1 = Enable local loopback mode, see loopback section and Figure 12.
MCR[5]: Xon-Any Enable (requires EFR bit-4=1)
* Logic 0 = Disable Xon-Any function (default). * Logic 1 = Enable Xon-Any function. In this mode, any RX character received will resume transmit operation.
The RX character will be loaded into the RX FIFO, unless the RX character is an Xon or Xoff character and the L222 is programmed to use the Xon/Xoff flow control.
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MCR[6]: Infrared Encoder/Decoder Enable (requires EFR bit-4=1) Infrared mode should be used on channel B only. This bit should remain a logic 0 for channel A.
* Logic 0 = Enable the standard modem receive and transmit input/output interface (default). * Logic 1 = Enable infrared IrDA receive and transmit inputs/outputs. The TX/RX output/input are routed to the
infrared encoder/decoder. The data input and output levels conform to the IrDA infrared interface requirement. While in this mode, the infrared TX output will be idling LOW. SEE "INFRARED MODE (UART CHANNEL B ONLY)" ON PAGE 22. MCR[7]: Clock Prescaler Select (requires EFR bit-4=1)
* Logic 0 = Divide by one. The input clock from the crystal or external clock is fed directly to the Programmable
Baud Rate Generator without further modification, i.e., divide by one (default).
* Logic 1 = Divide by four. The prescaler divides the input clock from the crystal or external clock by four and
feeds it to the Programmable Baud Rate Generator, hence, data rates become one forth. 4.8 Line Status Register (LSR) - Read Only
This register provides the status of data transfers between the UART and the host. LSR[0]: Receive Data Ready Indicator
* Logic 0 = No data in receive holding register or FIFO (default). * Logic 1 = Data has been received and is saved in the receive holding register or FIFO.
LSR[1]: Receiver Overrun Error Flag
* Logic 0 = No overrun error (default). * Logic 1 = Overrun error. A data overrun error condition occurred in the receive shift register. This happens
when additional data arrives while the FIFO is full. In this case the previous data in the receive shift register is overwritten. Note that under this condition the data byte in the receive shift register is not transferred into the FIFO, therefore the data in the FIFO is not corrupted by the error. LSR[2]: Receive Data Parity Error Tag
* Logic 0 = No parity error (default). * Logic 1 = Parity error. The receive character in RHR does not have correct parity information and is suspect.
This error is associated with the character available for reading in RHR. LSR[3]: Receive Data Framing Error Tag
* Logic 0 = No framing error (default). * Logic 1 = Framing error. The receive character did not have a valid stop bit(s). This error is associated with
the character available for reading in RHR. LSR[4]: Receive Break Error Tag
* Logic 0 = No break condition (default). * Logic 1 = The receiver received a break signal (RX was LOW for at least one character frame time). In the
FIFO mode, only one break character is loaded into the FIFO. LSR[5]: Transmit Holding Register Empty Flag This bit is the Transmit Holding Register Empty indicator. The THR bit is set to a logic 1 when the last data byte is transferred from the transmit holding register to the transmit shift register. The bit is reset to logic 0 concurrently with the data loading to the transmit holding register by the host. In the FIFO mode this bit is set when the transmit FIFO is empty, it is cleared when the transmit FIFO contains at least 1 byte.
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER LSR[6]: THR and TSR Empty Flag This bit is set to a logic 1 whenever the transmitter goes idle. It is set to logic 0 whenever either the THR or TSR contains a data character. In the FIFO mode this bit is set to a logic 1 whenever the transmit FIFO and transmit shift register are both empty. LSR[7]: Receive FIFO Data Error Flag
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* Logic 0 = No FIFO error (default). * Logic 1 = A global indicator for the sum of all error bits in the RX FIFO. At least one parity error, framing error
or break indication is in the FIFO data. This bit clears when there is no more error(s) in any of the bytes in the RX FIFO. 4.9 Modem Status Register (MSR) - Read Only
This register provides the current state of the modem interface input signals. Lower four bits of this register are used to indicate the changed information. These bits are set to a logic 1 whenever a signal from the modem changes state. These bits may be used for general purpose inputs when they are not used with modem signals. MSR[0]: Delta CTS# Input Flag
* Logic 0 = No change on CTS# input (default). * Logic 1 = The CTS# input has changed state since the last time it was monitored. A modem status interrupt
will be generated if MSR interrupt is enabled (IER bit-3). MSR[1]: Delta DSR# Input Flag
* Logic 0 = No change on DSR# input (default). * Logic 1 = The DSR# input has changed state since the last time it was monitored. A modem status interrupt
will be generated if MSR interrupt is enabled (IER bit-3). MSR[2]: Delta RI# Input Flag
* Logic 0 = No change on RI# input (default). * Logic 1 = The RI# input has changed from a LOW to HIGH, ending of the ringing signal. A modem status
interrupt will be generated if MSR interrupt is enabled (IER bit-3). MSR[3]: Delta CD# Input Flag
* Logic 0 = No change on CD# input (default). * Logic 1 = Indicates that the CD# input has changed state since the last time it was monitored. A modem
status interrupt will be generated if MSR interrupt is enabled (IER bit-3). MSR[4]: CTS Input Status CTS# pin may function as automatic hardware flow control signal input if it is enabled and selected by Auto CTS (EFR bit-7). Auto CTS flow control allows starting and stopping of local data transmissions based on the modem CTS# signal. A HIGH on the CTS# pin will stop UART transmitter as soon as the current character has finished transmission, and a LOW will resume data transmission. Normally MSR bit-4 bit is the complement of the CTS# input. However in the loopback mode, this bit is equivalent to the RTS# bit in the MCR register. The CTS# input may be used as a general purpose input when the modem interface is not used. MSR[5]: DSR Input Status Normally this bit is the complement of the DSR# input. In the loopback mode, this bit is equivalent to the DTR# bit in the MCR register. The DSR# input may be used as a general purpose input when the modem interface is not used.
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MSR[6]: RI Input Status Normally this bit is the complement of the RI# input. In the loopback mode this bit is equivalent to bit-2 in the MCR register. The RI# input may be used as a general purpose input when the modem interface is not used. MSR[7]: CD Input Status Normally this bit is the complement of the CD# input. In the loopback mode this bit is equivalent to bit-3 in the MCR register. The CD# input may be used as a general purpose input when the modem interface is not used. 4.10 Scratch Pad Register (SPR) - Read/Write
This is a 8-bit general purpose register for the user to store temporary data. The content of this register is preserved during sleep mode but becomes 0xFF (default) after a reset or a power off-on cycle. 4.11 Enhanced Mode Select Register (EMSR)
This register replaces SPR (during a Write) and is accessible only when FCTR[6] = 1. EMSR[1:0]: Receive/Transmit FIFO Level Count (Write-Only) When Scratchpad Swap (FCTR[6]) is asserted, EMSR bits 1-0 controls what mode the FIFO Level Counter is operating in. TABLE 12: SCRATCHPAD SWAP SELECTION
FCTR[6] EMSR[1] 0 1 1 1 X X 0 1 EMSR[0] Scratchpad is X 0 1 1 Scratchpad RX FIFO Level Counter Mode TX FIFO Level Counter Mode Alternate RX/TX FIFO Counter Mode
During Alternate RX/TX FIFO Level Counter Mode, the first value read after EMSR bits 1-0 have been asserted will always be the RX FIFO Level Counter. The second value read will correspond with the TX FIFO Level Counter. The next value will be the RX FIFO Level Counter again, then the TX FIFO Level Counter and so on and so forth. EMSR[3:2]: Reserved EMSR[5:4]: Extended RTS Hysteresis TABLE 13: AUTO RTS HYSTERESIS
EMSR BIT-5 0 0 0 0 0 0 0 0 EMSR BIT-4 0 0 0 0 1 1 1 1 FCTR BIT-1 0 0 1 1 0 0 1 1 FCTR BIT-0 0 1 0 1 0 1 0 1 RTS# HYSTERESIS (CHARACTERS) 0 4 6 8 8 16 24 32
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER TABLE 13: AUTO RTS HYSTERESIS
EMSR BIT-5 1 1 1 1 1 1 1 1 EMSR BIT-4 0 0 0 0 1 1 1 1 FCTR BIT-1 0 0 1 1 0 0 1 1 FCTR BIT-0 0 1 0 1 0 1 0 1 RTS# HYSTERESIS (CHARACTERS) 40 44 48 52 12 20 28 36
REV. 1.0.0
EMSR[6]: LSR Interrupt Mode
* Logic 0 = LSR Interrupt Delayed (for 16C2550 compatibility, default). LSR bits 2, 3, and 4 will generate an
interrupt when the character with the error is in the RHR.
* Logic 1 = LSR Interrupt Immediate. LSR bits 2, 3, and 4 will generate an interrupt as soon as the character is
received into the FIFO. EMSR[7]: 16X Sampling Rate Mode Logic 0 = 8X Sampling Rate. Logic 1 = 16X Sampling Rate (default). 4.12 FIFO Level Register (FLVL) - Read-Only
The FIFO Level Register replaces the Scratchpad Register (during a Read) when FCTR[6] = 1. Note that this is not identical to the FIFO Data Count Register which can be accessed when LCR = 0xBF. FLVL[7:0]: FIFO Level Register This register provides the FIFO counter level for the RX FIFO or the TX FIFO or both depending on EMSR[1:0]. See Table 12 for details. 4.13 Baud Rate Generator Registers (DLL, DLM and DLD) - Read/Write
These registers make-up the value of the baud rate divisor. The concatenation of the contents of DLM and DLL is a 16-bit value is then added to DLD/16 to achieve the fractional baud rate divisor. DLD must be enabled via EFR bit-4 before it can be accessed. SEE "PROGRAMMABLE BAUD RATE GENERATOR WITH FRACTIONAL DIVISOR" ON PAGE 11. 4.14 Device Identification Register (DVID) - Read Only
This register contains the device ID (0x0A for XR16V2751). Prior to reading this register, DLL and DLM should be set to 0x00 (DLD = 0xXX). 4.15 Device Revision Register (DREV) - Read Only
This register contains the device revision information. For example, 0x01 means revision A. Prior to reading this register, DLL and DLM should be set to 0x00 (DLD = 0xXX). 4.16 Trigger Level Register (TRG) - Write-Only
User Programmable Transmit/Receive Trigger Level Register. If both the TX and RX trigger levels are used, the TX trigger levels must be set before the RX trigger levels. TRG[7:0]: Trigger Level Register
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
These bits are used to program desired trigger levels when trigger Table-D is selected. FCTR bit-7 selects between programming the RX Trigger Level (a logic 0) and the TX Trigger Level (a logic 1). 4.17 RX/TX FIFO Level Count Register (FC) - Read-Only
This register is accessible when LCR = 0xBF. Note that this register is not identical to the FIFO Level Count Register which is located in the general register set when FCTR bit-6 = 1 (Scratchpad Register Swap). It is suggested to read the FIFO Level Count Register at the Scratchpad Register location when FCTR bit-6 = 1. See Table 12. FC[7:0]: RX/TX FIFO Level Count Receive/Transmit FIFO Level Count. Number of characters in Receiver FIFO (FCTR[7] = 0) or Transmitter FIFO (FCTR[7] = 1) can be read via this register. Reading this register is not recommended when transmitting or receiving data. 4.18 Feature Control Register (FCTR) - Read/Write
This register controls the XR16V2751 new functions that are not available in ST16C2450 or ST16C2550. FCTR[1:0]: RTS Hysteresis User selectable RTS# hysteresis levels for hardware flow control application. After reset, these bits are set to "0" to select the next trigger level for hardware flow control. See Table 13 for more details. FCTR[2]: IrDa RX Inversion
* Logic 0 = Select RX input as encoded IrDa data (Idle state will be LOW). * Logic 1 = Select RX input as inverted encoded IrDa data (Idle state will be HIGH).
FCTR[3]: Reserved For proper functionality, this bit should be a logic 0. FCTR[5:4]: Transmit/Receive Trigger Table Select See Table 10 for more details. TABLE 14: TRIGGER TABLE SELECT
FCTR BIT-5 0 0 1 1 FCTR BIT-4 0 1 0 1 TABLE Table-A (TX/RX) Table-B (TX/RX) Table-C (TX/RX) Table-D (TX/RX)
FCTR[6]: Scratchpad Swap
* Logic 0 = Scratch Pad register is selected as general read and write register. ST16C550 compatible mode. * Logic 1 = FIFO Level Count register (Read-Only), Enhanced Mode Select Register (Write-Only). Number of
characters in transmit or receive FIFO can be read via scratch pad register when this bit is set. Enhanced Mode Select Register is selected when it is written into. FCTR[7]: Programmable Trigger Register Select If using both programmable TX and RX trigger levels, TX trigger levels must be set before RX trigger levels.
* Logic 0 = Registers TRG and FC selected for RX. * Logic 1 = Registers TRG and FC selected for TX.
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER 4.19 Enhanced Feature Register (EFR)
REV. 1.0.0
Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive character software flow control selection (see Table 15). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes are selected, the double 8-bit words are concatenated into two sequential characters. Caution: note that whenever changing the TX or RX flow control bits, always reset all bits back to logic 0 (disable) before programming a new setting. EFR[3:0]: Software Flow Control Select Single character and dual sequential characters software flow control is supported. Combinations of software flow control can be selected by programming these bits. TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS
EFR BIT-3 CONT-3 0 0 1 0 1 X X X 1 EFR BIT-2 CONT-2 0 0 0 1 1 X X X 0 EFR BIT-1 CONT-1 0 X X X X 0 1 0 1 EFR BIT-0 CONT-0 0 X X X X 0 0 1 1 TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL No TX and RX flow control (default and reset) No transmit flow control Transmit Xon1, Xoff1 Transmit Xon2, Xoff2 Transmit Xon1 and Xon2, Xoff1 and Xoff2 No receive flow control Receiver compares Xon1, Xoff1 Receiver compares Xon2, Xoff2 Transmit Xon1, Xoff1 Receiver compares Xon1 or Xon2, Xoff1 or Xoff2 Transmit Xon2, Xoff2 Receiver compares Xon1 or Xon2, Xoff1 or Xoff2 Transmit Xon1 and Xon2, Xoff1 and Xoff2, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 No transmit flow control, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
0
1
1
1
1
1
1
1
0
0
1
1
EFR[4]: Enhanced Function Bits Enable Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-7, and DLD to be modified. After modifying any enhanced bits, EFR bit-4 can be set to a logic 0 to latch the new values. This feature prevents legacy software from altering or overwriting the enhanced functions once set. Normally, it is recommended to leave it enabled, logic 1.
* Logic 0 = modification disable/latch enhanced features. IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 57, and DLD are saved to retain the user settings. After a reset, the IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-7, and DLD are set to a logic 0 to be compatible with ST16C550 mode (default).
* Logic 1 = Enables the above-mentioned register bits to be modified by the user.
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EFR[5]: Special Character Detect Enable
* Logic 0 = Special Character Detect Disabled (default). * Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with
data in Xoff-2 register. If a match exists, the receive data will be transferred to FIFO and ISR bit-4 will be set to indicate detection of the special character. Bit-0 corresponds with the LSB bit of the receive character. If flow control is set for comparing Xon1, Xoff1 (EFR [1:0]= `10') then flow control and special character work normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]= `01') then flow control works normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special character interrupt, if enabled via IER bit-5. EFR[6]: Auto RTS Flow Control Enable RTS# output may be used for hardware flow control by setting EFR bit-6 to logic 1. When Auto RTS is selected, an interrupt will be generated when the receive FIFO is filled to the programmed trigger level and RTS de-asserts HIGH at the next upper trigger level or hysteresis level. RTS# will return LOW when FIFO data falls below the next lower trigger level. The RTS# output must be asserted (LOW) before the auto RTS can take effect. RTS# pin will function as a general purpose output when hardware flow control is disabled.
* Logic 0 = Automatic RTS flow control is disabled (default). * Logic 1 = Enable Automatic RTS flow control.
EFR[7]: Auto CTS Flow Control Enable Automatic CTS Flow Control.
* Logic 0 = Automatic CTS flow control is disabled (default). * Logic 1 = Enable Automatic CTS flow control. Data transmission stops when CTS# input de-asserts HIGH.
Data transmission resumes when CTS# returns LOW. 4.19.1 Software Flow Control Registers (XOFF1, XOFF2, XON1, XON2) - Read/Write
These registers are used as the programmable software flow control characters xoff1, xoff2, xon1, and xon2. For more details, see Table 7.
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B
REGISTERS DLM, DLL DLD RHR THR IER FCR ISR LCR MCR LSR MSR RESET STATE DLM = 0x00 and DLL = 0x01. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. Bits 7-0 = 0x00 Bits 7-0 = 0xXX Bits 7-0 = 0xXX Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x01 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x60 Bits 3-0 = Logic 0 Bits 7-4 = Logic levels of the inputs inverted Bits 7-0 = 0xFF Bits 7-0 = 0x80 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 RESET STATE RS-232 LOW or +5V RS-232 LOW or +5V RS-232 LOW or +5V CMOS/TTL HIGH (or VCC) Three-State Condition (16 mode) CMOS/TTL HIGH (68 mode)
REV. 1.0.0
SPR EMSR FLVL TRG FC FCTR EFR XON1 XON2 XOFF1 XOFF2 I/O SIGNALS TXDA/TXDB RTSA/RTSB DTRA/DTRB TXB INT (IRQ#)
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
ABSOLUTE MAXIMUM RATINGS
Power Supply Range Voltage at Any Pin Operating Temperature Storage Temperature Package Dissipation 5.5 Volts GND-0.3 V to 5.5 V -40o to +85oC -65o to +150oC 500 mW
TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: 15%)
Thermal Resistance (64-QFN) theta-ja = 40oC/W, theta-jc = 13oC/W
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA= -40O TO +85OC (INDUSTRIAL GRADE), VCC= 3.3 - 5.5V
SYMBOL REV. 1.0.0
PARAMETER
CONDITIONS
3.3V LIMITS MIN MAX
5.0V LIMITS MIN MAX
UNITS
DC CHARACTERISTICS
ICC Supply Current, Normal Mode VCC=3.3V to 5.5V, TA=+25C, no load 40 45 mA
ISLP/IPWS
Supply Current, Sleep Mode/PowerSave Mode
40
50
uA
OSCILLATOR INPUT (X1)
VILCK VIHCK Clock Input Low Level Clock Input High Level -0.3 2.4 0.6 VCC -0.5 3.0 0.6 VCC V V
LOGIC INPUTS/OUTPUTS (D[0:7], A[0:2], IOR#, IOW#/R/W#, CS#, INT/IRQ#, RST#/RST, I/M#, PWRSAVE, ACP, TXB, RXB, RXBSEL, FAST, R_EN
VIL VIH VOL VOH IIL IHL Input Low Voltage Input High Voltage Output Low Voltage Output High Voltage Input Low Leakage Current Input High Leakage Current 2.0 +/-10 +/-10 -0.3 2.0 0.7 5.5 0.4 2.0 +/-10 +/-10 -0.3 2.0 0.7 5.5 0.4 V V V V uA uA
RS-232 INPUTS (RXD, CTS, DSR, RI, DCD)
Input Voltage Range VIHR VILR VHYS RTR Input Threshold Low Input Threshold High Input Hysteresis Input Transmition Resistance TA=+25C 3 TA=+25C TA=+25C 0.6 2.0 0.5 7 3 +/-15 0.8 2.4 0.5 7 +/-15 V V V V Kohm
RS-232 OUTPUTS (TXD, RTS, DTR)
Output Voltage Range 3Kohm load on all transmitter outputs Vcc=0V, transmitter output=+/-2V +/-5.0 +/-5.0 V
ROR IOS ILKGR
Output Resistance Output Short-Circuit Current Output Leakage Current
300 +/-60
300 +/-60 +/-25
ohm mA uA
Vcc=0, transmitters disabled
+/-25
RS-232 AC TIMING (TXD)
Maximum Data Rate (FAST = GND) Transmitter Slew Rate (FAST = GND) Maximum Data Rate (FAST = VCC) Transmitter Slew Rate (FAST = VCC) RL=3Kohm, CL=1000pF CL = 50pF to 2500pF, RL=3-7Kohm RL=3Kohm, CL=1000pF CL = 50pF to 2500pF, RL=3-7Kohm 250 30 1 100 250 30 1 100 Kbps V/us Mbps V/us
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
AC ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA=-40O TO +85OC, VCC=3.3 - 5.5V, 70 PF LOAD WHERE APPLICABLE
SYMBOL PARAMETER MIN OSC CLK TAS TAH TCS TRD TDY TRDV TDD TWR TDY TDS TDH TADS TADH TRWS TRDA TRDH TWDS TWDH TRWH TCSL TCSD TWDO TMOD TRSI TSSI TRRI Crystal Frequency External Clock Frequency External Clock Low/High Time Address Setup Time (16 Mode) Address Hold Time (16 Mode) Chip Select Width (16 Mode) IOR# Strobe Width (16 Mode) Read Cycle Delay (16 Mode) Data Access Time (16 Mode) Data Disable Time (16 Mode) IOW# Strobe Width (16 Mode) Write Cycle Delay (16 Mode) Data Setup Time (16 Mode) Data Hold Time (16 Mode) Address Setup (68 Mode) Address Hold (68 Mode) R/W# Setup to CS# (68 Mode) Read Data Access (68 mode) Read Data Disable Time (68 mode) Write Data Setup (68 mode) Write Data Hold (68 Mode) CS# De-asserted to R/W# De-asserted (68 Mode) CS# Width (68 Mode) CS# Cycle Delay (68 Mode) Delay From IOW# To Output Delay To Set Interrupt From MODEM Input Delay To Reset Interrupt From IOR# Delay From Stop To Set Interrupt Delay From IOR# To Reset Interrupt 0 10 5 5 65 65 50 50 50 1 50 0 65 65 10 5 0 0 0 60 15 0 10 5 5 65 65 50 50 50 1 50 30 0 0 65 65 65 60 15 0 65 65 10 5 0 0 0 60 15 LIMITS 3.3 MAX 16 16 30 0 0 65 65 65 60 15 MIN LIMITS 5.0 MAX 16 16 MHz MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns Bclk ns UNIT
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER AC ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA=-40O TO +85OC, VCC=3.3 - 5.5V, 70 PF LOAD WHERE APPLICABLE
SYMBOL PARAMETER MIN TSI TINT TWRI TRST N Bclk Delay From Stop To Interrupt Delay From Initial INT Reset To Transmit Start Delay From IOW# To Reset Interrupt Reset Pulse Width Baud Rate Divisor Baud Clock 40 1 216-1 8 LIMITS 3.3 MAX 50 24 50 40 1 216-1 8 MIN LIMITS 5.0 MAX 50 24 50 ns Bclk ns ns Hz UNIT
REV. 1.0.0
16X or 8X of data rate
FIGURE 13. CLOCK TIMING
CLK CLK
EXTERNAL CLOCK
OSC
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XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
FIGURE 14. MODEM INPUT/OUTPUT TIMING
IOW#
T WDO RTS# DTR# Change of state Change of state
CD# CTS# DSR# T MOD INT
Change of state
Change of state
T MOD Activ e T RSI Activ e Activ e
IOR#
Activ e
Activ e
Activ e T MOD
RI#
Change of state
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER FIGURE 15. 16 MODE (INTEL) DATA BUS READ TIMING
REV. 1.0.0
A0A2 TAS
Valid Address TAH TAS
Valid Address TAH
TCS CS#
TCS
TDY TRD IOR# TRD
TRDV D0-D7 Valid Data
TDD
TRDV Valid Data
TDD
RDTm
FIGURE 16. 16 MODE (INTEL) DATA BUS WRITE TIMING
A0A2 TAS
Valid Address TAH TAS
Valid Address TAH
TCS CS#
TCS
TDY TWR IOW# TWR
TDS D0-D7 Valid Data
TDH
TDS Valid Data
TDH
16Write
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REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
FIGURE 17. 68 MODE (MOTOROLA) DATA BUS READ TIMING
A0-A2 TADS
Valid Address
Valid Address
TCSL
TADH
CS# TRWS TCSD
R/W#
TRWH
TRDH TRDA D0-D7 Valid Data Valid Data
68Read
FIGURE 18. 68 MODE (MOTOROLA) DATA BUS WRITE TIMING
A0-A2 TADS
Valid Address
Valid Address
TCSL
TADH
CS# TRWS TCSD
R/W#
TRWH
TWDS D0-D7 Valid Data
T WDH
Valid Data
68Write
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XR19L222
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER FIGURE 19. RECEIVE READY INTERRUPT TIMING [NON-FIFO MODE]
RX
Start Bit Stop Bit TSSR 1 Byte in RHR
REV. 1.0.0
D0:D7
D0:D7 TSSR 1 Byte in RHR
D0:D7 TSSR 1 Byte in RHR
INT
TRR
TRR
TRR
IOR#
(Reading data out of RHR)
RXNFM
FIGURE 20. TRANSMIT READY INTERRUPT TIMING [NON-FIFO MODE]
TX
(Unloading) IER[1] enabled Start Bit Stop Bit
D0:D7
D0:D7
D0:D7
ISR is read
ISR is read
ISR is read
INT*
TWRI TSRT TWRI TSRT TWRI TSRT
IOW#
(Loading data into THR)
TXNonFIFO
*INT is cleared when the ISR is read or when data is loaded into the THR.
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
FIGURE 21. RECEIVE READY INTERRUPT TIMING [FIFO MODE]
Start Bit
RX
S D0:D7 Stop Bit
S D0:D7 T
D0:D7
TSSI
S D0:D7 T
S D0:D7 T S D0:D7 T
S D0:D7 T
RX FIFO drops below RX Trigger Level
INT
TSSR
RX FIFO fills up to RX Trigger Level or RX Data Timeout
IOR#
(Reading data out of RX FIFO)
TRRI
RXINTDMA#
FIGURE 22. TRANSMIT READY INTERRUPT TIMING [FIFO MODE]
Start Bit Stop Bit Last Data Byte Transmitted S D0:D7 T S D0:D7 T TSI T S D0:D7 T S D0:D7 T ISR is read S D0:D7 T
TX FIFO Empty
TX
S D0:D7 T IER[1] enabled
ISR is read
INT*
TX FIFO fills up to trigger level TX FIFO drops below trigger level
TWRI
IOW#
(Loading data into FIFO)
TX INT
*INT is cleared when the ISR is read or when TX FIFO fills up to the trigger level.
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TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
REV. 1.0.0
PACKAGE DIMENSIONS (64 PIN QFN - 9 X 9 X 0.9 mm)
Note: the actual center pad is metallic and the size (D2) is device-dependent with a typical tolerance of 0.3mm
Note: The control dimension is in millimeter. INCHES SYMBOL MIN MAX MILLIMETERS MIN MAX
A A1 A3 D D2 b e L k
0.031 0.000 0.006 0.350 0.295 0.007
0.039 0.002 0.010 0.358 0.307 0.012
0.80 0.00 0.15 8.90 7.50 0.18
1.00 0.05 0.25 9.10 7.80 0.30
0.0197 BSC 0.012 0.008 0.020 -
0.50 BSC 0.35 0.20 0.45 -
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REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
DATE
REVISION
DESCRIPTION
June 2006 October 2006 January 2007 May 2007
P1.0.0 P1.0.1 P1.0.2 1.0.0
Preliminary Datasheet Updated Package Dimensions Updated EIA/TIA-232-F compliant voltage range to +3.3V to +5.5V. Final Datasheet. Updated DC Electrical Characteristics. Updated QFN drawing.
NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Copyright 2007 EXAR Corporation Datasheet May 2007. Send your UART technical inquiry with technical details to hotline: uarttechsupport@exar.com. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
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REV. 1.0.0
TABLE OF CONTENTS
GENERAL DESCRIPTION ................................................................................................ 1
APPLICATIONS............................................................................................................................................... 1 FEATURES .................................................................................................................................................... 1
FIGURE 1. BLOCK DIAGRAM ............................................................................................................................................................. 1 FIGURE 2. PIN OUT OF THE DEVICE.................................................................................................................................................. 2 ORDERING INFORMATION................................................................................................................................ 2
PIN DESCRIPTIONS ....................................................................................................... 3
1.0 PRODUCT DESCRIPTION....................................................................................................................... 7 2.0 FUNCTIONAL DESCRIPTIONS............................................................................................................... 8
2.1 CPU INTERFACE................................................................................................................................................. 8
FIGURE 3. XR19L222 TYPICAL INTEL/MOTOROLA DATA BUS INTERCONNECTIONS ............................................................................. 8
2.2 5-VOLT TOLERANT INPUTS .............................................................................................................................. 2.3 DEVICE HARDWARE RESET ............................................................................................................................. 2.4 DEVICE IDENTIFICATION AND REVISION........................................................................................................ 2.5 CHANNEL A AND B SELECTION.......................................................................................................................
9 9 9 9
TABLE 1: CHANNEL A AND B SELECT IN 16 MODE ............................................................................................................................ 9 TABLE 2: CHANNEL A AND B SELECT IN 68 MODE ............................................................................................................................ 9
2.6 CHANNEL A AND B INTERNAL REGISTERS ................................................................................................... 9 2.7 DMA MODE........................................................................................................................................................ 10 2.8 INT (IRQ#) OUTPUT .......................................................................................................................................... 10
TABLE 3: INT (IRQ#) PIN OPERATION FOR TRANSMITTER ............................................................................................................... 10 TABLE 4: INT (IRQ#) PIN OPERATION FOR RECEIVER .................................................................................................................... 10
2.9 CRYSTAL OR EXTERNAL CLOCK INPUT ...................................................................................................... 10
FIGURE 4. TYPICAL CRYSTAL CONNECTIONS................................................................................................................................... 11
2.10 PROGRAMMABLE BAUD RATE GENERATOR WITH FRACTIONAL DIVISOR.......................................... 11
FIGURE 5. BAUD RATE GENERATOR ............................................................................................................................................... 12 TABLE 5: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING ................................................... 13
2.11 TRANSMITTER ................................................................................................................................................ 14
2.11.1 TRANSMIT HOLDING REGISTER (THR) - WRITE ONLY ......................................................................................... 2.11.2 TRANSMITTER OPERATION IN NON-FIFO MODE .................................................................................................. FIGURE 6. XR19L222 TRANSMITTER AND RECEIVER ...................................................................................................................... FIGURE 7. TRANSMITTER OPERATION IN NON-FIFO MODE .............................................................................................................. 2.11.3 TRANSMITTER OPERATION IN FIFO MODE ........................................................................................................... FIGURE 8. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE ..................................................................................... 2.12.1 RECEIVE HOLDING REGISTER (RHR) - READ-ONLY ............................................................................................ 2.12.2 SELECTABLE INPUT TO RX OF CHANNEL B ......................................................................................................... FIGURE 9. RECEIVER OPERATION IN NON-FIFO MODE .................................................................................................................... FIGURE 10. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE ....................................................................... 14 14 14 15 15 15 16 16 16 17
2.12 RECEIVER ....................................................................................................................................................... 15
2.13 AUTO RTS (HARDWARE) FLOW CONTROL ............................................................................................... 17 2.14 AUTO RTS HYSTERESIS............................................................................................................................... 17 2.15 AUTO CTS FLOW CONTROL ........................................................................................................................ 18
FIGURE 11. AUTO RTS AND CTS FLOW CONTROL OPERATION....................................................................................................... 18
2.16 AUTO XON/XOFF (SOFTWARE) FLOW CONTROL..................................................................................... 19
TABLE 6: AUTO XON/XOFF (SOFTWARE) FLOW CONTROL ............................................................................................................... 19
2.17 SPECIAL CHARACTER DETECT .................................................................................................................. 19 2.18 SLEEP MODES AND POWER-SAVE FEATURE WITH WAKE-UP INTERRUPT ........................................ 20
2.18.1 PARTIAL SLEEP MODE............................................................................................................................................. 2.18.1.1 UART IN SLEEP MODE, RS-232 TRANSCEIVER ACTIVE......................................................................................... 2.18.1.2 UART ACTIVE, CHARGE PUMP OF RS-232 TRANSCEIVER SHUT DOWN .................................................................. 2.18.2 FULL SLEEP MODE ................................................................................................................................................... 2.18.3 POWER-SAVE FEATURE .......................................................................................................................................... 20 20 21 21 21
2.19 INFRARED MODE (UART CHANNEL B ONLY)............................................................................................. 22
FIGURE 12. INTERNAL LOOP BACK ................................................................................................................................................. 22
3.0 UART INTERNAL REGISTERS ............................................................................................................. 23
TABLE 7: UART INTERNAL REGISTERS .................................................................................................................................... 23 TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1 ......................................... 24
4.0 INTERNAL REGISTER DESCRIPTIONS............................................................................................... 25
4.1 RECEIVE HOLDING REGISTER (RHR) - READ- ONLY .................................................................................. 25
I
XR19L222
REV. 1.0.0
TWO CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
4.2 TRANSMIT HOLDING REGISTER (THR) - WRITE-ONLY ............................................................................... 25 4.3 INTERRUPT ENABLE REGISTER (IER) - READ/WRITE ................................................................................ 25
4.3.1 IER VERSUS RECEIVE FIFO INTERRUPT MODE OPERATION ............................................................................... 26 4.3.2 IER VERSUS RECEIVE/TRANSMIT FIFO POLLED MODE OPERATION.................................................................. 26
4.4 INTERRUPT STATUS REGISTER (ISR) - READ-ONLY .................................................................................. 27
4.4.1 INTERRUPT GENERATION: ........................................................................................................................................ 27 4.4.2 INTERRUPT CLEARING: ............................................................................................................................................. 28 TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL ....................................................................................................................... 28
4.5 FIFO CONTROL REGISTER (FCR) - WRITE-ONLY ........................................................................................ 28
TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION .......................................................................... 30
4.6 LINE CONTROL REGISTER (LCR) - READ/WRITE ........................................................................................ 30
TABLE 11: PARITY SELECTION ........................................................................................................................................................ 31
4.7 MODEM CONTROL REGISTER (MCR) OR GENERAL PURPOSE OUTPUTS CONTROL - READ/WRITE . 4.8 LINE STATUS REGISTER (LSR) - READ ONLY.............................................................................................. 4.9 MODEM STATUS REGISTER (MSR) - READ ONLY ....................................................................................... 4.10 SCRATCH PAD REGISTER (SPR) - READ/WRITE ....................................................................................... 4.11 ENHANCED MODE SELECT REGISTER (EMSR) .........................................................................................
32 33 34 35 35
TABLE 12: SCRATCHPAD SWAP SELECTION .................................................................................................................................... 35 TABLE 13: AUTO RTS HYSTERESIS ................................................................................................................................................ 35
4.12 FIFO LEVEL REGISTER (FLVL) - READ-ONLY ............................................................................................ 4.13 BAUD RATE GENERATOR REGISTERS (DLL, DLM AND DLD) - READ/WRITE ....................................... 4.14 DEVICE IDENTIFICATION REGISTER (DVID) - READ ONLY....................................................................... 4.15 DEVICE REVISION REGISTER (DREV) - READ ONLY................................................................................. 4.16 TRIGGER LEVEL REGISTER (TRG) - WRITE-ONLY .................................................................................... 4.17 RX/TX FIFO LEVEL COUNT REGISTER (FC) - READ-ONLY ....................................................................... 4.18 FEATURE CONTROL REGISTER (FCTR) - READ/WRITE ..........................................................................
36 36 36 36 36 37 37
TABLE 14: TRIGGER TABLE SELECT ............................................................................................................................................... 37
4.19 ENHANCED FEATURE REGISTER (EFR) ..................................................................................................... 38
TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS ........................................................................................................................ 38 4.19.1 SOFTWARE FLOW CONTROL REGISTERS (XOFF1, XOFF2, XON1, XON2) - READ/WRITE .............................. 39 TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B ............................................................................................ 40
ABSOLUTE MAXIMUM RATINGS ................................................................................. 41 TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: 15%) 41
AC ELECTRICAL CHARACTERISTICS............................................................................................................. 43
Unless otherwise noted: TA=-40o to +85oC, Vcc=3.3 - 5.5V, 70 pF load where applicable.................................... 43
FIGURE 13. CLOCK TIMING............................................................................................................................................................. FIGURE 14. MODEM INPUT/OUTPUT TIMING .................................................................................................................................... FIGURE 15. 16 MODE (INTEL) DATA BUS READ TIMING ................................................................................................................... FIGURE 16. 16 MODE (INTEL) DATA BUS WRITE TIMING ................................................................................................................. FIGURE 17. 68 MODE (MOTOROLA) DATA BUS READ TIMING .......................................................................................................... FIGURE 18. 68 MODE (MOTOROLA) DATA BUS WRITE TIMING......................................................................................................... FIGURE 19. RECEIVE READY INTERRUPT TIMING [NON-FIFO MODE] ............................................................................................... FIGURE 20. TRANSMIT READY INTERRUPT TIMING [NON-FIFO MODE] ............................................................................................. FIGURE 21. RECEIVE READY INTERRUPT TIMING [FIFO MODE] ....................................................................................................... FIGURE 22. TRANSMIT READY INTERRUPT TIMING [FIFO MODE] ..................................................................................................... 44 45 46 46 47 47 48 48 49 49
PACKAGE DIMENSIONS (64 PIN QFN - 9 X 9 X 0.9 mm).............................................. 50 TABLE OF CONTENTS ..................................................................................................... I
II

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