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FM30C256
256Kb Data Collector Features
256K bit Ferroelectric Nonvolatile RAM * Organized as 32,768 x 8 bits * High Endurance 10 Billion (1010) Read/Writes * 10 year Data Retention * NoDelayTM Writes * Advanced High-Reliability Ferroelectric Process Fast Two-wire Serial Interface * Up to 1 MHz Maximum Bus Frequency * Supports Legacy Timing for 100 kHz & 400 kHz * Clock Registers Accessed via 2-wire Interface Real-time Clock/Calendar * Backup Current under 1 A * Tracks Seconds through Centuries (BCD format) * Tracks Leap Years through 2099 * Uses Standard 32.768 kHz Crystal (6pF) * Software Calibration System Supervisor * Active-low Reset Output for VDD Out-of-Tolerance * Tamper Detect Input with Battery Backup and Time Stamp
Description
The FM30C256 is a 256-kilobit data collection subsystem including nonvolatile RAM, timekeeping, CPU supervisor, and system tamper detection. Nonvolatile RAM is provided by FRAM technology, which is ideal for collection data and requires no battery backup for nonvolatile storage. In other respects, it provides the same features as SRAM. FRAM performs write operations at bus speed with no write delays. Write cycles can be continuous without block limitations. In addition, it offers much higher write endurance than other nonvolatile memories. The FM30C256 supports up to 1010 read/write cycles. The FM30C256 also includes timekeeping with external battery backup. The timekeeper consists of registers that represent time and date information in BCD format. The clock includes a calibration mode that allows a software adjustment for timekeeping accuracy. To maintain system data integrity, the FM30C256 provides a reset signal asserted when VDD is out of tolerance. /RST remains active for 100 ms after VDD returns to proper levels. The FM30C256 also provides a battery-backed tamper detect circuit that records a rising edge on the TIN input. A batterybacked flag is set when the event occurs, but can only be cleared by software. The FM30C256 is provided in a 20-pin SOIC package and is guaranteed over an industrial temperature range of -40C to +85C.
Pin Configuration
TIN A0 A1 A2 NC NC NC CAL RST VSS
1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11
VDD SCL SDA NC NC NC NC X2 X1 VBAK
Pin Names TIN A0-A2 CAL /RST X1, X2 SDA SCL VDD VBAK VSS
Function Tamper Detect input Device Select inputs Clock Calibration output Reset Output Crystal Connections Serial Data Serial Clock Supply Voltage 5V Battery-Backup input Ground
Ordering Information
FM30C256-S 20-pin SOIC
This product conforms to specifications per the terms of the Ramtron standard warranty. Production processing does not necessarily include testing of all parameters. Rev 2.1 Dec. 2002
Ramtron International Corporation 1850 Ramtron Drive, Colorado Springs, CO 80921 (800) 545-FRAM, (719) 481-7000, Fax (719) 481-7058
www.ramtron.com
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FM30C256
Address Latch & Counter
32K x 8 FRAM Array
A2-A0 SDA SCL Protocol & Device Select Serial to Parallel Converter
8 Data Latch
VDD VBAK RST
32.768 kHz
Power Isolation Power Management RTC Address Latch & Counter
Battery-backed power
X1 X2 TIN CAL RTC Oscillator Counters
Real-time Clock Registers
Tamper Latch
Tamper Flag
Figure 1. Block Diagram Pin Descriptions Pin Name A2-A0 Type Input Pin Description Device select inputs are used to address the part on a serial bus. To select the device, the address value on the three pins must match the corresponding bits contained in the device address. Note that these are not address pins for read/write operations. The address pins are pulled down internally. Tamper detect is a battery backed input that stores a 1 in the Flags/Control register when it detects a rising edge on the TIN pin. 512 Hz square-wave output for clock calibration 32.768 kHz crystal connection. When using an external oscillator source, use X2 as the oscillator input and leave X1 floating. Active low reset output (open drain) Serial Data Address. This is a bi-directional line for the two-wire interface. It is open-drain and is intended to be wire-OR'd with other devices on the two-wire bus. The input buffer incorporates a Schmitt trigger for noise immunity and the output driver includes slope control for falling edges. A pull-up resistor is required. Serial Clock. The serial clock line for the two-wire interface. Data is clocked out of the part on the falling edge, and in on the rising edge. The SCL input also incorporates a Schmitt trigger input for noise immunity. Battery backup supply voltage (3V) Supply Voltage (5V) Ground No connect
TIN CAL X1, X2 /RST SDA
Input Output I/O Output I/O
SCL VBAK VDD VSS NC
Input Supply Supply Supply -
Rev 2.1 Dec. 2002
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FM30C256
Overview
The FM30C256 data collector combines a 256Kb serial nonvolatile RAM with a real-time clock (RTC), a power monitor, and a tamper detect circuit. The FM30C256 integrates these complementary but distinct functions under a common interface in a single package. Despite providing multiple interface Ids as explained below, the product is a single monolithic device. The memory is organized as 32Kx8 of FRAM and is accessed via a separate 2-wire device ID from the remaining functions. This allows the user to preserve addressing information when switching between memory and RTC functions. Modularity in software design is preserved as well. The real-time clock function and the tamper detection is accessed under its own 2-wire device ID. This allows clock data to be read while maintaining the last (most recently used) memory address in the other device. The clock and tamper functions are controlled by 9 registers that are backed up by the external battery. Clock and tamper functions continue to operate from battery power when VDD drops below the battery voltage. In addition to the software-controlled functions, the FM30C256 also provides reset signal for an external microcontroller host. This signal is asserted when VDD drops below the specified trip point (VTP). It
remains asserted until VDD returns above VTP for the hold-off period (tRPU). The power monitor has no interaction with other software-controlled functions. Any access to the device will be ignored when VDD < VTP.
Memory Operation
When accessing the FM30C256, the user addresses 32,768 locations each with 8 data bits. These data bits are shifted in and out serially. The 32,768 addresses are accessed using the two-wire protocol, which includes a slave address (to distinguish from other non-memory devices), and an extended 16-bit address. The decoder uses only the lower 15 bits for accessing the memory. The upper address bit should be set to 0 for compatibility with larger devices in the future. The memory is read or written at the speed of the two-wire bus. The interface protocol is described further below.
RTC Register Map
The interface to clock and tamper functions is via 9 address locations mapped to a separate 2-wire device ID. The interface protocol is described below. The registers contain timekeeping data, control bits, or information flags. A short description of each register follows. Detailed descriptions follow the register summary section.
Register Map Summary Table
D7 D6 D5 Data D4 D3 ILLEGAL ADDRESSES D2 years months date 0 day hours minutes seconds CAL2 CAL1 CAL W D1 D0 Function Years Month Date Day Hours Minutes Seconds CAL/Control Flags/Control Range 00-99 1-12 1-31 1-7 0-23 0-59 0-59
Address 9-F 8 7 6 5 4 3 2 1 0
10 years 0 0 0 0 0 0 /OSCEN Tamper 0 0 0 0 10 mo 10 date 0 0 10 hours 10 minutes 10 seconds CALS CAL4 reserved reserved 0
TSEN CF
CAL3 TST
CAL0 R
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FM30C256
Table 1. Register Map
Address 8h Description Timekeeping - Years
D7
10 year.3
D6
10 year.2
D5
10 year.1
D4
10 year.0
D3
Year.3
D2
Year.2
D1
Year.1
D0
Year.0
Contains the lower two BCD digits of the year. Lower nibble contains the value for years; upper nibble contains the value for 10s of years. Each nibble operates from 0 to 9. The range for the register is 0-99.
7h
Timekeeping - Months
D7
0
D6
0
D5
0
D4
10 Month
D3
Month.3
D2
Month.2
D1
Month.1
D0
Month.0
Contains the BCD digits for the month. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble (one bit) contains the upper digit and operates from 0 to 1. The range for the register is 1-12.
6h
Timekeeping - Date of the month
D7
0
D6
0
D5
10 date.1
D4
10 date.0
D3
Date.3
D2
Date.2
D1
Date.1
D0
Date.0
Contains the BCD digits for the date of the month. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper digit and operates from 0 to 3. The range for the register is 131.
5h
Timekeeping - Day of the week
D7
0
D6
0
D5
0
D4
0
D3
0
D2
Day.2
D1
Day.1
D0
Day.0
Lower nibble contains a value that correlates to day of the week. Day of the week is a ring counter that counts from 1 to 7 then returns to 1. The user must assign meaning to the day value, as the day is not integrated with the date.
4h
Timekeeping - Hours
D7
0
D6
0
D5
10 hours.1
D4
10 hours.0
D3
Hours.3
D2
Hours2
D1
Hours.1
D0
Hours.0
Contains the BCD value of hours in 24-hour format. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble (two bits) contains the upper digit and operates from 0 to 2. The range for the register is 0-23.
3h
Timekeeping - Minutes
D7
0
D6
10 min.2
D5
10 min.1
D4
10 min.0
D3
Min.3
D2
Min.2
D1
Min.1
D0
Min.0
Contains the BCD value of minutes. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper minutes digit and operates from 0 to 5. The range for the register is 0-59.
2h
Timekeeping - Seconds
D7
0
D6
10 sec.2
D5
10 sec.1
D4
10 sec.0
D3
Seconds.3
D2
Seconds.2
D1
Seconds.1
D0
Seconds.0
Contains the BCD value of seconds. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper digit and operates from 0 to 5. The range for the register is 0-59.
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FM30C256 Address 1h Description CAL/Control
D7
OSCEN
D6
TSEN
D5
CALS
D4
CAL.4
D3
CAL.3
D2
CAL.2
D1
CAL.1
D0
CAL.0
/OSCEN TSEN CALS CAL.4-0
/Oscillator Enable. When set to 1, the oscillator is halted. When set to 0, the oscillator runs. Disabling the oscillator can save battery power during storage. On a power-up without battery, this bit is set to 1. Time Stamp Enable. When set to 1, a Tamper Detect event will record the date and time of the event. On a power-up without battery, this bit is set to 0. Calibration sign. Determines if the calibration adjustment is applied as an addition to or as a subtraction from the time-base. Calibration is explained below. These five bits control the calibration of the clock.
0h
Flags/Control
D7
Tamper
D6
CF
D5
Reserved
D4
Reserved
D3
TST
D2
CAL
D1
W
D0
R
Tamper CF
TST CAL W R
Reserved
Tamper Detect. This bit is set to 1 when rising edge is detected on the TIN pin. It can only be cleared to 0 by the user. Century Overflow Flag. This bit is set to a 1 when the values in the years register overflows from 99 to 00. This indicates a new century, such as going from 1999 to 2000 or 2099 to 2100. The user should record the new century information as needed. This bit is cleared to 0 when the Flag register is read. It is read-only for the user. Invokes factory test mode. Users should always set this bit to 0. Calibration Mode. When set to 1, the clock enters calibration mode. When CAL is set to 0, the clock operates normally, and the CAL pin is driven low. Write Time. Setting the W bit to 1 freezes updates of the timekeeping registers. The user can then write them with updated values. Setting the W bit to 0 causes the contents of the time registers to be transferred to the timekeeping counters. Read Time. Setting the R bit to 1 copies a static image of the timekeeping registers and places them in a holding register. The user can then read them without concerns over changing values causing system errors. The R bit going from 0 to 1 causes the timekeeping capture, so the bit must be returned to 0 prior to reading again. Reserved bits. Do not use. Should remain set to 0.
Real-time Clock Operation
The real-time clock (RTC) consists of an oscillator, divider, and a register system for accessing the information. It divides down the 32.768 kHz timebase and provides a minimum resolution of seconds (1Hz) to the user. Static registers provide the user with read/write access to the time values. The synchronization of these registers with the timekeeper core is performed using R and W bits in register 0. Changing the R bit from 0 to 1 causes a transfer of the timekeeping information to holding registers that can be read by the user. If a timekeeper update is pending when R is set, then the update will be completed prior to loading the registers. Another update cannot be performed until the R bit is cleared to 0. Setting the W bit to 1 causes the timekeeper to freeze updates. Clearing it to 0 causes the values in the time
Rev 2.1 Dec. 2002
registers to be written into the timekeeper core. Users should be certain not to load invalid values, such as FFh, to the timekeeping registers. Updates to the timekeeping core occur continuously except when frozen. A diagram of the timekeeping core follows. Backup Power The real-time clock/calendar is intended for permanently powered operation. When the primary system power fails, the voltage on the VDD pin will drop. When VDD is less than the voltage on the VBAK pin, the clock will switch to the backup power supply. The clock operates at extremely low current in order to maximize battery life. However, an advantage of combining a clock function with FRAM is that the 256K memory data is not lost regardless of the backup power source.
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FM30C256
512 Hz
W
Oscillator 32.768 kHz crystal Years 8 bits Months 5 bits Date 6 bits Hours 6 bits
Clock Divider
1 Hz
Update Logic
CF
Minutes 7 bits
Seconds 7 bits
Days 3 bits
User Interface Registers
R
Figure 2. Real-time Clock Core Block Diagram 2.17 ppm or 0.09 minutes per month at the calibrated temperature. The calibration setting is battery backed and is stored in bits CAL.4-0. This value only can be written when the CAL bit is set to a 1. To exit the calibration mode, the user must clear the CAL bit to a 0. When the CAL bit is 0, the CAL pin will be driven low. When the calibration mode is entered, the user can measure the frequency error on the CAL pin. This error expressed in ppm translates directly into timekeeping error. An offsetting calibration adjustment corrects this error. However, the correction is applied by adding or removing pulses on a periodic basis. Therefore, the correction will not appear on the 512 Hz output. The calibration correction must be applied using the lookup table below. The timekeeping accuracy can be verified by comparing the FM30C256 time to a reference source.
Calibration When the CAL bit in register 0 is set to 1, the clock enters calibration mode. Calibration operates by applying a digital correction to the counter based on the frequency error. In CAL mode, the CAL pin is driven with a 512 Hz (nominal) square wave. Any measured deviation from 512 Hz is converted to an error in ppm. This error corresponds to a correction value that is then written by the user into the calibration register. The correction factors are listed in the table below. Positive ppm errors require a negative adjustment that removes pulses. Negative ppm errors require a positive correction that adds pulses. Positive ppm adjustments have the CALS bit set to 1, where as negative ppm adjustments have CALS = 0. After calibration, the clock will have a maximum error of
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FM30C256 Table 2. Calibration Adjustments Positive Calibration for slow clocks: Calibration will achieve +/- 2.17 PPM after calibration Measured Frequency Range Error Range (PPM) Min Max Min Max Program Calibration Register to: 0 512.0000 511.9989 0 2.17 000000 1 511.9989 511.9967 2.18 6.51 100001 2 511.9967 511.9944 6.52 10.85 100010 3 511.9944 511.9922 10.86 15.19 100011 4 511.9922 511.9900 15.20 19.53 100100 5 511.9900 511.9878 19.54 23.87 100101 6 511.9878 511.9856 23.88 28.21 100110 7 511.9856 511.9833 28.22 32.55 100111 8 511.9833 511.9811 32.56 36.89 101000 9 511.9811 511.9789 36.90 41.23 101001 10 511.9789 511.9767 41.24 45.57 101010 11 511.9767 511.9744 45.58 49.91 101011 12 511.9744 511.9722 49.92 54.25 101100 13 511.9722 511.9700 54.26 58.59 101101 14 511.9700 511.9678 58.60 62.93 101110 15 511.9678 511.9656 62.94 67.27 101111 16 511.9656 511.9633 67.28 71.61 110000 17 511.9633 511.9611 71.62 75.95 110001 18 511.9611 511.9589 75.96 80.29 110010 19 511.9589 511.9567 80.30 84.63 110011 20 511.9567 511.9544 84.64 88.97 110100 21 511.9544 511.9522 88.98 93.31 110101 22 511.9522 511.9500 93.32 97.65 110110 23 511.9500 511.9478 97.66 101.99 110111 24 511.9478 511.9456 102.00 106.33 111000 25 511.9456 511.9433 106.34 110.67 111001 26 511.9433 511.9411 110.68 115.01 111010 27 511.9411 511.9389 115.02 119.35 111011 28 511.9389 511.9367 119.36 123.69 111100 29 511.9367 511.9344 123.70 128.03 111101 30 511.9344 511.9322 128.04 132.37 111110 31 511.9322 511.9300 132.38 136.71 111111
Negative Calibration for fast clocks: Calibration will achieve +/- 2.17 PPM after calibration Measured Frequency Range Error Range (PPM) Min Max Min Max Program Calibration Register to: 0 512.0000 512.0011 0 2.17 000000 1 512.0011 512.0033 2.18 6.51 000001 2 512.0033 512.0056 6.52 10.85 000010 3 512.0056 512.0078 10.86 15.19 000011 4 512.0078 512.0100 15.20 19.53 000100 5 512.0100 512.0122 19.54 23.87 000101 6 512.0122 512.0144 23.88 28.21 000110 7 512.0144 512.0167 28.22 32.55 000111 8 512.0167 512.0189 32.56 36.89 001000
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FM30C256
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 512.0189 512.0211 512.0233 512.0256 512.0278 512.0300 512.0322 512.0344 512.0367 512.0389 512.0411 512.0433 512.0456 512.0478 512.0500 512.0522 512.0544 512.0567 512.0589 512.0611 512.0633 512.0656 512.0678 512.0211 512.0233 512.0256 512.0278 512.0300 512.0322 512.0344 512.0367 512.0389 512.0411 512.0433 512.0456 512.0478 512.0500 512.0522 512.0544 512.0567 512.0589 512.0611 512.0633 512.0656 512.0678 512.0700 36.90 41.24 45.58 49.92 54.26 58.60 62.94 67.28 71.62 75.96 80.30 84.64 88.98 93.32 97.66 102.00 106.34 110.68 115.02 119.36 123.70 128.04 132.38 41.23 45.57 49.91 54.25 58.59 62.93 67.27 71.61 75.95 80.29 84.63 88.97 93.31 97.65 101.99 106.33 110.67 115.01 119.35 123.69 128.03 132.37 136.71 001001 001010 001011 001100 001101 001110 001111 010000 010001 010010 010011 010100 010101 010110 010111 011000 011001 011010 011011 011100 011101 011110 011111
Tamper Detection and Time Stamp The TIN pin is a battery-backed input that is used to detect a tamper event in the system. When a rising edge occurs on TIN, this Tamper Detect event is recorded in the MSB of register 0. This action will occur only when either VBAK or VDD is applied. Any further activity on TIN, such as a falling edge, will be ignored. The user is responsible for reading and clearing the Tamper flag. Clearing the Tamper flag allows the TIN to detect another rising edge. The tamper flag can only be read or cleared when VDD 4.5V. On a power-up without battery, this bit is set to zero. The tamper input TIN can be used to timestamp the exact time a tamper event occurs. This feature can be enabled by setting the timestamp enable bit TSEN in the calibration control register (RTC address 1, bit D6). At power-up, TSEN is cleared and must be set by the user. When a rising edge occurs on TIN and the TSEN bit is set, the date and time of the event will be recorded. The current time is loaded into the timekeeping registers. When the system is checked for a tamper event, the time of the event can be read. After a tamper event, the timekeeping registers can be overwritten if the R bit is set before reading the timekeeping registers. To prevent overwriting the timestamp, the control register should be read first to check that the tamper bit is set. If it is set, the
Rev 2.1 Dec. 2002
timekeeping registers should be read to collect the time of the last tamper event. Checking for a tamper event before setting the R bit will ensure accurate tamper timestamp information. If the TSEN bit is not set, then a rising edge on TIN will not trigger a timestamp. System Reset Control The /RST pin allows the user to easily control a system level reset function. It is an open drain output and requires an external pullup resistor to VDD for proper operation. When VDD is within the specified operating range, /RST output is tri-stated and pulled to VDD by the external resistor. If VDD drops below the reset trip point voltage level (VTP) and remains below this level for the VTP noise immunity duration (tRNR), the /RST pin will be driven low. It will continue to drive low until VDD falls below the VRST level. When VDD rises again above VTP, /RST will continue to drive low for a duration (tRPU) to ensure a robust system reset at a reliable VDD level. After tRPU has been met, the /RST pin tri-states and is pulled high by the external pullup resistor. Refer to the figure on page 16 for a graphical description of the /RST function and timing.
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FM30C256
Two-wire Interface
The FM30C256 employs an industry standard twowire bus that is familiar to many users and for convenience is described in this section. The FM30C256 is unique since it incorporates two logical devices in one chip. Each logical device can be accessed individually. One is a memory device. It has a Slave Address (Slave ID = 1010b) that operates the same as a stand-alone memory device. The second device is a real-time clock and tamper detect which share a unique Slave Address (Slave ID = 1101b). By convention, any device that is sending data onto the bus is the transmitter while the target device for this data is the receiver. The device that is controlling the bus is the master. The master is responsible for generating the clock signal for all operations. Any device on the bus that is being controlled is a slave. The FM30C256 is always a slave device. The bus protocol is controlled by transition states in the SDA and SCL signals. There are four conditions: Start, Stop, Data bit, and Acknowledge. Figure 4 illustrates the signal conditions that specify the four states. Detailed timing diagrams are shown in the electrical specifications. Start Condition A Start condition is indicated when the bus master drives SDA from high to low while the SCL signal is high. All read and write transactions begin with a Start condition. An operation in progress can be aborted by asserting a Start condition at any time. Aborting an operation using the Start condition will ready the FM30C256 for a new operation. If the power supply drops below the specified VDD minimum during operation, the system should issue a Start condition prior to performing another operation.
Stop Condition A Stop condition is indicated when the bus master drives SDA from low to high while the SCL signal is high. All operations must end with a Stop condition. If an operation is pending when a stop is asserted, the operation will be aborted. The master must have control of SDA (not a memory read) in order to assert a Stop condition. Data/Address Transfer All data transfers (including addresses) take place while the SCL signal is high. Except under the two conditions described above, the SDA signal should not change while SCL is high. Acknowledge The Acknowledge takes place after the 8th data bit has been transferred in any transaction. During this state the transmitter must release the SDA bus to allow the receiver to drive it. The receiver drives the SDA signal low to acknowledge receipt of the byte. If the receiver does not drive SDA low, the condition is a No-Acknowledge and the operation is aborted. The receiver might fail to acknowledge for two distinct reasons. First is that a byte transfer fails. In this case, the No-Acknowledge ends the current operation so that the part can be addressed again. This allows the last byte to be recovered in the event of a communication error. Second and most common, the receiver does not send an Acknowledge to deliberately terminate an operation. For example, during a read operation, the FM30C256 will continue to place data onto the bus as long as the receiver sends Acknowledges (and clocks). When a read operation is complete and no more data is needed, the receiver must not acknowledge the last byte. If the receiver acknowledges the last byte, this will cause the FM30C256 to attempt to drive the bus on the next clock while the master is sending a new command such as a Stop.
SCL SDA Stop (Master) Start (Master) 7 6 0 Data bit Acknowledge (Transmitter) (Receiver)
Data bits (Transmitter)
Figure 3. Data Transfer Protocol
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FM30C256 Slave Address The first byte that the FM30C256 expects after a Start condition is the slave address. As shown in Figure 4, the slave address contains the Slave ID, Device Select address, and a bit that specifies if the transaction is a read or a write. The FM30C256 has two Slave Addresses (Slave IDs) associated with two logical devices. To access the memory device, bits 7-4 should be set to 1010b. See Figure 4. The other logical device within the FM30C256 is the real-time clock and tamper detect. To access this device, bits 7-4 of the slave address should be set to 1101b. A bus transaction with this slave address will not affect the memory in any way. See Figure 5. The Slave ID bits allow other function types to reside on the 2-wire bus for a given device select address. The device select bits (bits 3-1) are used to select one of eight chips on a two-wire bus. They must match the corresponding value on the external address pins in order to select the device. Up to eight devices can reside on the same two-wire bus by assigning a different address to each device. Bit 0 is the read/write bit. A "1" indicates a read operation, and a "0" indicates a write operation. LSB (lower byte) which contains the remaining eight address bits. The address is latched internally. Each access causes the latched address to be incremented automatically. The current address is the value that is held in the latch, either a newly written value or the address following the last access. The current address will be held as long as power remains or until a new value is written. Accesses to the clock do not affect the current memory address. Reads always use the current address. A random read address can be loaded by beginning a write operation as explained below. After transmission of each data byte, just prior to the Acknowledge, the FM30C256 increments the internal address. This allows the next sequential byte to be accessed with no additional addressing externally. After the last address (7FFFh) is reached, the address latch will roll over to 0000h. There is no limit to the number of bytes that can be accessed with a single read or write operation. Addressing Overview - RTC The RTC operates in a similar manner to the memory, except that it uses only one byte of address. The low four bits of address specify register 0-8, and the upper four bits are "don't care". Only addresses 0 through 8 should be loaded during an RTC write command. Loading addresses 9-F is an illegal condition and should not be attempted since unpredictable results could occur. Data Transfer After the address information has been transmitted, data transfer between the bus master and the FM30C256 begins. For a read, the FM30C256 will place 8 data bits on the bus then wait for an Acknowledge from the master. If the Acknowledge occurs, the FM30C256 will transfer the next byte. If the Acknowledge is not sent, the FM30C256 will end the read operation. For a write operation, the FM30C256 will accept 8 data bits from the master then send an Acknowledge. All data transfer occurs MSB (most significant bit) first. Memory Write Operation All memory writes begin with a Slave Address, then a memory address. The bus master indicates a write operation by setting the slave address LSB to a 0. After addressing, the bus master sends each byte of data to the memory and the memory generates an Acknowledge condition. Any number of sequential bytes may be written. If the end of the address range is reached internally, the address counter will wrap from 7FFFh to 0000h. Internally, the actual memory write occurs after the 8th data bit is transferred. It will
Slave ID
1 7 0 6 1 5 0 4
Device Select A2 A1 A0
3 2 1 R/W 0
Figure 4. Slave Address - Memory
Slave ID
1 7 1 6 0 5 1 4
Device Select A2
3
A1 A0
2 1
R/W 0
Figure 5. Slave Address - RTC
Addressing Overview - Memory After the FM30C256 acknowledges the Slave Address, the master can place the memory address on the bus for a write operation. The address requires two bytes. The first is the MSB (upper byte). Since the device uses only 15 address bits, the value of the upper bit is a "don't care". Following the MSB is the
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FM30C256 be complete before the Acknowledge is sent. Therefore, if the user desires to abort a write without altering the memory contents, this should be done using a Start or Stop condition prior to the 8th data bit. Figures 6 and 7 illustrate a single- and multiplewrites to memory.
By Master
Start
Address & Data
Stop
S
Slave Address
0A
Address MSB
A
Address LSB
A
Data Byte
A
P
By FM30C256
Acknowledge
Figure 6. Single Byte Memory Write
Start By Master Address & Data Stop
S
Slave Address
0A
Address MSB
A
Address LSB
A
Data Byte
A
Data Byte
A
P
By FM30C256
Acknowledge
Figure 7. Multiple Byte Memory Write
Memory Read Operation There are two types of memory read operations. They are current address read and selective address read. In a current address read, the FM30C256 uses the internal address latch to supply the address. In a selective read, the user performs a procedure to set the address to a specific value. Current Address & Sequential Read As mentioned above the FM30C256 uses an internal latch to supply the address for a read operation. A current address read uses the existing value in the address latch as a starting place for the read operation. The system reads from the address immediately following that of the last operation. To perform a current address read, the bus master supplies a slave address with the LSB set to 1. This indicates that a read operation is requested. After receiving the complete device address, the FM30C256 will begin shifting data out from the current address on the next clock. The current address is the value held in the internal address latch. Beginning with the current address, the bus master can read any number of bytes. Thus, a sequential read is simply a current address read with multiple byte transfers. After each byte the internal address counter will be incremented.
Each time the bus master acknowledges a byte, this indicates that the FM30C256 should read out the next sequential byte. There are four ways to terminate a read operation. Failing to properly terminate the read will most likely create a bus contention as the FM30C256 attempts to read out additional data onto the bus. The four valid methods follow. 1. The bus master issues a No-Acknowledge in the 9th clock cycle and a Stop in the 10th clock cycle. This is illustrated in the diagrams below. This is preferred. The bus master issues a No-Acknowledge in the 9th clock cycle and a start in the 10th. The bus master issues a Stop in the 9th clock cycle. The bus master issues a Start in the 9th clock cycle.
2. 3. 4.
If the internal address reaches 7FFFh, it will wrap around to 0000h on the next read cycle. Figures 8 and 9 show the proper operation for current address reads. Selective (Random) Read There is a simple technique that allows a user to select a random address location as the starting point for a read operation. This involves using the first
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FM30C256 three bytes of a write operation to set the internal address followed by subsequent read operations. To perform a selective read, the bus master sends out the slave address with the LSB set to 0. This specifies a write operation. According to the write protocol, the bus master then sends the address bytes that are loaded into the internal address latch. After the FM30C256 acknowledges the address, the bus master issues a Start condition. This simultaneously aborts the write operation and allows the read command to be issued with the slave address LSB set to a 1. The operation is now a read from the current address. Figure 10 shows the proper operation for a selective read. RTC Write Operation All RTC writes operate in a similar manner to memory writes. The distinction is that a different device ID is used and only one byte address is needed instead of two. Figure 11 illustrates a single byte write to the clock. RTC Read Operation As with writes, a read operation begins with the Slave Address. To perform a register read, the bus master supplies a Slave Address with the LSB set to 1. This indicates that a read operation is requested. After receiving the complete Slave Address, the FM30C256 will begin shifting data out from the current register address on the next clock. Autoincrement operates for the RTC address as with the memory address. A current address read for the RTC looks exactly like the memory except that the device ID is different. The FM30C256 contains two separate address registers, one for the 256K memory address and the other for the RTC register address. This allows the contents of one address register to be modified without affecting the current address of the other register. For example, this would allow an interrupted read to the memory while still providing fast access to an RTC register. A subsequent memory read will then continue from the memory address where it previously left off, without requiring the load of a new memory address. However, a write sequence always requires an address to be supplied.
By Master
Start
Address
No Acknowledge Stop
S By FM30C256
Slave Address
1A
Data Byte
1
P
Acknowledge
Data
Figure 8. Current Address Memory Read
By Master
Start
Address
Acknowledge
No Acknowledge Stop
S By FM30C256
Slave Address
1A
Data Byte
A
Data Byte
1P
Acknowledge
Data
Figure 9. Sequential Memory Read
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FM30C256
Start By Master Address Start Address
No Acknowledge Stop
S
Slave Address
0A
Address MSB
A
Address LSB
A
S
Slave Address
1A
Data Byte
1P
By FM30C256
Acknowledge
Data
Figure 10. Selective (Random) Memory Read
By Master
Start
Address & Data
Stop
S By FM30C256
Slave Address
0 A XXXX
Address
A
Data Byte
A
P
Acknowledge
Figure 11. Byte RTC Write
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FM30C256
Electrical Specifications
Absolute Maximum Ratings Symbol Description VDD Power Supply Voltage with respect to VSS VIN Voltage on any signal pin with respect to VSS TSTG TLEAD Storage temperature Lead temperature (Soldering, 10 seconds) Ratings -1.0V to +7.0V -1.0V to +7.0V and VIN < VDD+1.0V -55C to + 125C 300 C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only, and the functional operation of the device at these or any other conditions above those listed in the operational section of this specification is not implied. Exposure to absolute maximum ratings conditions for extended periods may affect device reliability.
DC Operating Conditions (TA = -40 C to + 85 C, VDD = 4.5V to 5.5V unless otherwise specified) Symbol Parameter Min Typ Max VDD Main Power Supply 4.5 5.0 5.5 IDD VDD Supply Current @ SCL = 100 kHz 300 @ SCL = 400 kHz 650 @ SCL = 1 MHz 1.35 ISB Standby Current 150 VBAK Clock Backup Voltage 2.5 3.0 3.5 IBAK Clock Backup Current 1 VTP VDD trip point voltage that activates /RST 4.2 4.5 1.2 VRST VDD min for Active /RST @ IOL = 80 A, VOL = 0.4V ILI Input Leakage Current 10 ILO Output Leakage Current 10 VIL Input Low Voltage -0.3 0.3 VDD VIH Input High Voltage 0.7 VDD VDD + 0.5 VILB Input Low Voltage (TIN) -0.3 0.5 for VDD < VBAK VIHB Input High Voltage (TIN) VBAK + 0.5 VBAK - 0.5 for VDD < VBAK VOL Output Low Voltage (CAL, /RST, SDA) 0.4 @ IOL = 3 mA 2.4 VOH Output High Voltage (CAL) @ IOH = -2 mA RIN Address Input Resistance (A2-A0) for VIN = VIL (max) 20 for VIN = VIH (min) 1 VHYS Input Hysteresis 0.05 VDD Notes 1. SCL toggling between VDD-0.3V and VSS, other inputs VSS or VDD-0.3V 2. SCL = SDA = VDD. All inputs at VSS or VDD. Stop command issued. 3. VIN or VOUT = VSS to VDD. Does not apply to pins with internal pull down resistors. 4. This parameter is characterized but not tested. 5. VBAK = 3.0V, VDD < VBAK; oscillator running. 6. /RST is asserted active when VDD < VTP. 7. The minimum VDD to guarantee the level of /RST remains a valid VOL level.
Units V A A mA A V A V V A A V V V V V V K M V
Notes 1
2 5 6 7 3 3
4 4
4
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FM30C256 AC Parameters (TA = -40 C to + 85 C, VDD = 4.5V to 5.5V, CL = 100 pF unless otherwise specified) Symbol Parameter Min Max Min Max Min Max fSCL SCL Clock Frequency 0 100 0 400 0 1000 tLOW Clock Low Period 4.7 1.3 0.6 tHIGH Clock High Period 4.0 0.6 0.4 tAA SCL Low to SDA Data Out Valid 3 0.9 0.55 tBUF tHD:STA tSU:STA Units kHz s s s Notes
Bus Free Before New Transmission 4.7 1.3 0.5 s Start Condition Hold Time 4.0 0.6 0.25 s Start Condition Setup for Repeated 4.7 0.6 0.25 s Start tHD:DAT Data In Hold 0 0 0 ns tSU:DAT Data In Setup 250 100 100 ns tR Input Rise Time 1000 300 300 ns tF Input Fall Time 300 300 100 ns tSU:STO Stop Condition Setup 4.0 0.6 0.25 s tDH Data Output Hold 0 0 0 ns (from SCL @ VIL) tSP Noise Suppression Time Constant 50 50 50 ns on SCL, SDA Notes: All SCL specifications as well as start and stop conditions apply to both read and write operations.
1 This parameter is periodically sampled and not 100% tested.
1 1
Power Cycle Timing (TA = -40 C to + 85 C) Symbol Parameter tRPU Reset active after VDD>VTP tRNR VDD < VTP noise immunity tR Rise time of VDD from VBAK to VTP tF Fall time of VDD from VTP to VBAK Notes
1 2
Min 100 10 100 100
Typ -
Max 200 25
Units ms s s s
Notes 1 1,2 1,2
This parameter is periodically sampled and not 100% tested. Slew rate for proper transition between the battery-backed and normal operation.
Data Retention (VDD = 4.5V to 5.5V unless otherwise specified) Parameter Min Units Notes Data Retention 10 Years 1 Notes 1. The relationship between retention, temperature, and the associated reliability level is
characterized separately.
Capacitance (TA = 25 C, f=1.0 MHz, VDD = 5V) Symbol Parameter CIO Input/output capacitance (SDA) CI Input capacitance CXTAL X1, X2 Crystal pin capacitance Notes
1 2
Max 8 6 12
Units pF pF pF
Notes 1 1 1, 2
This parameter is periodically sampled and not 100% tested. The crystal attached to the X1/X2 pins must be rated as 6pF.
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FM30C256 AC Test Conditions Input Pulse Levels Input rise and fall times Input and output timing levels 0.1 VDD to 0.9 VDD 10 ns 0.5 VDD Equivalent AC Load Circuit
5.5V
1700
Diagram Notes All start and stop timing parameters apply to both read and write cycles. Clock specifications are identical for read and write cycles. Write timing parameters apply to slave address, word address, and write data bits. Functional relationships are illustrated in the relevant data sheet sections. These diagrams illustrate the timing parameters only. Read Bus Timing
tR
Output 100 pF
tF
t HIGH
t LOW
t SP
t SP
SCL
t SU:SDA t BUF 1/fSCL t HD:DAT t SU:DAT t DH
SDA Start Stop Start
t AA
Acknowledge
Write Bus Timing
t HD:DAT
SCL
t SU:STO t HD:STA t SU:DAT t AA
SDA Start Stop Start Acknowledge
/RST Timing
VDD VTP VBAK VRST
tF
tR
tRPU
RST
tRNR
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FM30C256 20-pin SOIC (JEDEC Standard MS-013 Variation AC)
E
H
h 45
Pin 1
D A e B A1
L
C
0.10 mm 0.004 in.
Controlling dimensions in millimeters. Conversions to inches are not necessarily exact. Symbol Dim Min Nom. A mm 2.35 in. 0.093 A1 mm 0.10 in. 0.004 B mm 0.33 in. 0.013 C mm 0.23 in. 0.009 D mm 12.60 in. 0.496 E mm 7.40 7.50 in. 0.291 0.295 e mm 1.27 BSC in. 0.050 BSC H mm 10.00 in. 0.393 L mm 0.40 in. 0.016 0
Max 2.65 0.104 0.30 0.012 0.51 0.020 0.32 0.013 13.00 0.512 7.60 0.299 10.65 0.419 1.27 0.05 8
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FM30C256
Revision History
Revision 0.1 0.2 Date 5/10/01 9/17/01 Summary Initial Release Updated package & pinout. Changed Idd and Capacitance specifications. CAL pin changed from open drain to push/pull. CAL pin drives low when CAL bit is reset. TIN pin powered by VBAK, added DC specs for TIN. Timestamp feature added to Tamper Detect. Changed test load to 1700 ohms to reflect 3mA VOL test condition. Changed to production status. Updated package drawing. Increased storage temperature range. Changed VTP (max) and IOL condition. Modified block diagram and pin description to clarify crystal pins X1, X2.
2.0 2.0A 2.1
2/18/02 4/17/02 12/16/02
Rev 2.1 Dec. 2002
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