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| 19-2150; Rev 0; 8/01 MAX6900 Evaluation System General Description The MAX6900 evaluation system (EV system) is a realtime clock evaluation system consisting of a MAX6900 evaluation kit (EV kit) and a Maxim MAXSMBus module. Windows(R) 98 software provides a handy user interface to exercise the features of the MAX6900. (Note: Windows NT/2000 requires additional driver software; contact factory.) This EV kit is intended to demonstrate the functionality and features of the MAX6900 real-time clock with an I2CTM-compatible 2-wire interface. It is not designed to exercise the MAX6900 at its maximum serial bus interface speed. A typical bus interface speed is in the 90kHz range and depends upon the operating system and computer used. Order the complete EV system (MAX6900EVSYS) for comprehensive evaluation of the MAX6900 using a PC. Order the EV kit (MAX6900EVKIT) if the MAXSMBus module has already been purchased with a previous Maxim EV system, or for custom use in other C-based systems. o Proven PC Board Layout o Low-Voltage Operation o Supply Current Monitoring o Fully Assembled and Tested Features Evaluates: MAX6900 Ordering Information PART MAX6900EVKIT MAX6900EVSYS TEMP. RANGE 0C to +70C 0C to +70C INTERFACE User supplied Windows software Component List REFERENCE C1, C3, C4 C2, C5 J1 JU1, JU2 R1, R2 R3 U1 U2, U3 Y1 QTY 3 2 1 2 0 1 1 2 1 DESCRIPTION 0.1F, 10V X7R ceramic capacitors 10F, 10V tantalum capacitors 2 x 10 right-angle socket SamTec SSW-110-02-S-D-RA 2-pin jumpers Open (site for optional 4.7k 5% 1206 resistor) 49.9k 1% resistor MAX6900EUT MAX3370EXK-T 32.768kHz crystal, 12.5pF load capacitance Digi-Key X801-ND 32.768kHz crystal, 12.5pF load capacitance PC board, MAX6900 EV kit 3.5in software disk, MAX6900 EV kit Quick Start Recommended Equipment Before you begin, the following equipment is needed: * Maxim MAX6900EVKIT and MAXSMBus interface board * * * * 12VDC power supply (any supply voltage between +9V and +15V is acceptable) Computer running Windows 98 Spare parallel port 25-pin I/O extension cable Connections and Setup 1) With the power off, connect the 12VDC power supply to the MAXSMBus board between POS9 and GND. The MAX6900 IC's +5V supply comes from the MAXSMBus board. 2) Connect the boards together. 3) Connect the 25-pin I/O extension cable from the computer's parallel port to the MAXSMBus board. The EV kit software uses a loopback connection to confirm that the correct port has been selected. 4) Install the EV system software on your computer by running the INSTALL.EXE program on the floppy disk. The program files are copied and icons are created for them in the Windows Start menu. 1 Y2 None None 0 1 1 Windows is a registered trademark of Microsoft Corp. I2C is a registered trademark of Philips Corp. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. MAX6900 Evaluation System Evaluates: MAX6900 Table 1. Jumper Functions JUMPER JU1 JU1 JU2 JU2 POSITION Closed* Open Closed* Open VL = +5V from MAXSMBus module User-supplied VL +5V The supply current-sensing resistor R3 is shorted, enabling communication with the real-time clock. The timekeeping supply current can be estimated by measuring voltage across R3. Communication is not possible in this state. FUNCTION *An asterisk indicates a default configuration. 5) Ensure that the jumper settings are in the default position (Table 1). 6) Start the program by opening its icon in the Start menu. 7) Click on the Set from computer's clock button to write the current time of day into the MAX6900. 8) Observe the difference between the computer's time and the MAX6900 time. 9) Unplug the MAX6900EVSYS from the parallel port for long-term drift testing. an optional surface-mount crystal. Only one crystal may be used. MAXSMBus Connector The MAXSMBus board connects to the device under test in accordance with Table 2. Troubleshooting Problem: Unable to communicate while measuring supply current. Jumper JU2 must be closed to enable communication. Detailed Description of Hardware The MAX6900 (U1) is a real-time clock with RAM. The MAX3370 level translators (U2 and U3) are not required for normal operation of the MAX6900, but allow operation at supply voltages down to +2V, while still communicating with the MAXSMBus board, which is using +5V logic levels. See Figure 6, and refer to the MAX6900 data sheet. Detailed Description of Software The EV software provides access to all registers. The main timekeeping registers appear in the main screen, with other screens accessible from the View menu. To write to a single register, click on the appropriate register select button, set the desired value, and then click the Write button. Cyclic Burst Read must be disabled before you can write to a single register. To read a register, click on the appropriate register select button, and then click the Read button. Measuring Timekeeping Supply Current The MAX6900 is in standby mode whenever no commands are being sent. To measure the timekeeping supply current drawn in standby mode, first ensure that the main screen's Cyclic Burst Read checkbox is not checked, remove the shunt from jumper JU2, and measure the voltage across resistor R3. A voltage drop of 10mV represents 200nA of timekeeping supply current. For active bus operation (serial bus activity), replace shunt JU2 to prevent excessive voltage drop across resistor R3. Main Screen The Read button reads the most recently selected timekeeping register. The Write button writes the most recently selected timekeeping register. The Burst Read button performs a Burst Read from the timekeeping registers (except Century). The Burst Write button performs a Burst Write to the timekeeping registers (except Century). The Set from computer's clock button writes the PC's time into the MAX6900. The Cyclic Burst Read checkbox tells the software to perform a Burst Read from the timekeeping registers, at a rate of approximately 4 times per second. Updates are shown in the register display, along with the difference between MAX6900 time and the host PC's time (Figure 1). Surface-Mount Crystal The EV kit comes with a 1.1mm cylindrical tuning-fork crystal; however, the PC board layout accommodates 2 _______________________________________________________________________________________ MAX6900 Evaluation System Table 2. MAXSMBUS Connector Signals PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 NAME +5V GND SDA GND GND GND SCL GND SMBSUS GND ALERT GND ALERT2 GND OUTA GND OUTB GND GND RAW PWR I2C INTERFACE Optional +5V supply Ground SDA Ground Ground Ground SCL Ground No connection Ground No connection Ground No connection Ground No connection Ground No connection Ground Ground No connection that the corresponding bit is a logic 1. The Read button updates the most recently selected Setup register's checkboxes. The Write button writes the most recently selected Setup register (Figure 3). Evaluates: MAX6900 Auxiliary Functions 2-Wire Diagnostic The transition from evaluation to custom software development requires access to the low-level interface. Access the 2-wire diagnostic from the main screen's View menu. The 2-wire Diagnostic screen allows you to send generalpurpose SMBus commands. The Hunt for active devices button scans the entire address space, reporting each address that is acknowledged. The two most-often-used protocols are SMBusReadByte and SMBusWriteByte. SMBusReadByte transmits the device address, a command or register select byte, then re-transmits the device address and reads 1 byte. SMBusWriteByte transmits the device address, a command or register select byte, and 1 byte of data (Figure 4). SPI/3-Wire Diagnostic The transition from evaluation to custom software development requires access to the low-level interface. Access the SPI/3-wire diagnostic from the main screen's View menu. The SPI/3-Wire Diagnostic screen allows you to send SPI or 3-wire commands, or manipulate the parallel port pins directly. Each of the 25 pins is represented by a checkbox. A checkmark means that the corresponding pin is at a logic-high level. Pins that are inputs to the PC are grayed. The bit-banging SPI diagnostic transmits data using synchronous serial format (similar to Motorola's 68HC11 SPI interface). The SPI interface sends and receives data simultaneously on separate pins. Parallel port pin 2 drives the clock, pin 1 drives DIN, pin 4 drives chip select, and pin 11 senses DOUT. Pins 2, 4, and 11 are inverted by open-collector drivers, while pin 1 drives DIN directly. The 3-wire interface uses a bidirectional data pin. The MAXSMBus board implements the 3-wire interface by using an open-collector driver. Pin 2 drives the clock, pin 3 drives data, pin 4 drives chip select, and pin 11 senses data. All these signals are inverted by the opencollector drivers. The least-significant bit (LSB) is transmitted first, and (CPOL = 1, CPHA = 0) mode is used (Figure 5). Note: Odd-numbered pins are on the outer row. Even-numbered pins are on the inner row. The Hour register setting can be switched from 12hr format to 24hr format by clicking the -->24 button. RAM Screen The Single Read button reads the most recently selected RAM location. The Single Write button writes the most recently selected RAM location. The Burst Read button performs a Burst Read from the entire RAM. The Burst Write button performs a Burst Write to the RAM. Normally, all 31 locations are read, but the Burst Write length can be reduced. Burst Write always begins with RAM location 0. The Preset Data button performs a Burst Write to the RAM, setting all data to the same value (Figure 2). Setup Screen Each Setup register is represented by a group of eight checkboxes, one for each bit. A checkmark indicates _______________________________________________________________________________________ 3 MAX6900 Evaluation System Evaluates: MAX6900 Figure 1. Main Screen Figure 2. RAM Screen Figure 3. Setup Screen 4 _______________________________________________________________________________________ MAX6900 Evaluation System Evaluates: MAX6900 Figure 4. 2-Wire Diagnostic Figure 5. SPI/3-Wire Diagnostic _______________________________________________________________________________________ 5 MAX6900 Evaluation System Evaluates: MAX6900 VL VCC 5 R1 OPEN SCL SCL VCC 4 VCC VL 1 2 VL R3 49.9k JU2 C1 0.1F U2 MAX3370 IO_VCC GND 1 3 VL 5 SCL VCC X2 3 4 3 Y1 Y2 1 X1 4 2 2 I/O_VL U1 MAX6900 C3 0.1F 6 SDA 5 R2 OPEN SDA SDA VCC VL 1 2 C4 0.1F 4 U3 MAX3370 IO_VCC GND I/O_VL 3 VCC J1-1 J1-3 J1-5 J1-7 J1-9 J1-11 J1-13 J1-15 J1-17 J1-19 NC NC NC NC NC TO MAXSMBus BOARD J1-2 SDA J1-4 J1-6 SCL J1-8 J1-10 J1-12 J1-14 J1-16 J1-18 J1-20 NC GND VL VCC JU1 VL VCC C5 10F 10V C2 10F 10V Figure 6. MAX6900 EV Kit Schematic 6 _______________________________________________________________________________________ MAX6900 Evaluation Kit Evaluates: MAX6900 1.0" 1.0" Figure 7. MAX6900 EV Kit Component Placement Guide-- Component Side Figure 8. MAX6900 EV Kit PC Board Layout--Component Side 1.0" Figure 9. MAX6900 EV Kit PC Board Layout--Solder Side Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ______________________7 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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