Two-Wire Interface Board MAXSMBus interface between IBM-compatibl

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Two-Wire Interface Board MAXSMBus interface between IBM-compatibl

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19-1306; 3/98
Two-Wire Interface Board
MAXSMBus interface between IBM-compatible System Management (SMBus)TMcompatible serial-interface devices such temperature monitors, voltage regulators, converters (ADCs). MAXSMBus interface board connected between parallel port device under test, converting parallel data into two-wire, open-drain serial data. board provided with selected Maxim products intended replace commercially available SMBus hardware. MAXSMBus shipped with companion board, including relevant software.
_Features
SMBus-Compatible Two-Wire Interface SMBus Suspend Output SMBus Alert Inputs Overvoltage Fault Protection Parallel Port Interface
Evaluates: MAXSMBus
_Ordering Information
PART MAXSMBus BOARD TYPE Companion Board SMBus Kits
Maxim SMBus Interface Board _Component List
DESIGNATION C4-C9 R10, R4-R7 NONE DESCRIPTION 0.1µF ceramic capacitors 3.3µF, tantalum capacitors 1N5235B zener diode, 6.8V 1N5229B zener diode, 4.3V 1N4148 small signal diode DB25 right angle plug installed right angle male header 47k, resistors 4.7k, resistors resistors 74HC05 open-collector inverter 74HC04 inverter 74HC08 quad gate 74HC74 dual flip-flop +5V, 100mA regulator, LM78L05ACM MAX865EUA µMAX) MAX367CWN board
_MAXSMBus Functionality Check
Follow these steps verify that MAXSMBus interface board functioning properly. necessary software supplied disk with companion kit. Instructions operating software included manual. Connect supply (+7V minimum, +20V maximum) MAXSMBus interface board terminals labeled "POS9" "GND" lower left corner board. digital voltmeter verify that oval labeled "POS5" (+4.75V minimum, +5.25V maximum). Also verify that pads labeled "SBDAT1," "SBCLK1," "SBSUS1," "ALERT1," "ALERT2" above +4V. these voltages correct, MAXSMBus passes functionality test.
_Detailed Description
MAXSMBus interface board provides interface signals necessary interface PCcompatible computer with SMBus-compliant device. DB25 right-angle plug connects computer (Table companion board plugs into 20-pin dual-row right-angle header edge board (Table Alternatively, connection made soldering wires oval pads appropriate. This allows companion board placed environmental chamber evaluation over temperature. Refer documentation companion Maxim quick start operating instructions.
SMBus trademark Intel Corp. Maxim Integrated Products
free samples latest literature: http://www.maxim-ic.com, phone 1-800-998-8800. small orders, phone 408-737-7600 ext. 3468.
Two-Wire Interface Board Evaluates: MAXSMBus
Power Supply
interface board powered 78L05 linear regulator. companion board draw about 20mA power through circuit protector. Companion boards that require more power must provide their regulator. unregulated input 78L05 available right-angle header.
Driving Circuitry
74HC05 open-drain inverter (U1) used pull down SMBus interface signals. 74HC08 (U3), 74HC74 (U4), 74HC04 (U2) buffer signal provide capability mask ALERT interrupts, detect externally generated start condition, capture data sent external master. Interface connections listed Table Table
Fault Protection Circuitry
Overvoltage fault protection provided MAX367 fault protector (U7). SMBus interface signals exceed MAX367's power supply rails, MAX367 increases resistance prevent damage user's computer. MAX865 dual charge pump (U6) zener diodes provide supplies MAX367, thus allowing signals pass with nominal resistance 100.
Monitoring Circuitry
Flip-flop detects start condition (falling edge SMBDATA when SMBCLK high). Flip-flop detects falling SMBCLK edge when enabled, holds SMBCLK until software releases advance next data bit, software uses assert then release SMBCLK. logic high input also resets flip-flop U4B. Because parallel port limited number inputs, start-detect circuit alert inputs share single interrupt input. source interrupt distinguished using U3A, U3B, U3C.
_Troubleshooting Guide
SYMPTOMS CAUSE Board connected parallel printer port SOLUTION Verify that cable 25-pin parallel port extension cable with plug socket other end. Verify that cable connected printer port, floppy disk, SCSI, serial communications port. Check power connections interface board. Check clock data signal connections. operating interface board without companion Maxim evaluation kit-this should cause address-not-acknowledged symptom described below. Verify that companion board connected MAXSMBus interface board. Verify that companion board powered. companion offers choice addresses, confirm that software hardware addresses match. Some devices only read address select pins device power-up. Disable print manager Windows printer control panel. Disable printer driver. computer with commercially available BIOS. Make bootable floppy disk, remove unnecessary device drivers from A:config.sys, boot system from floppy.
Can't Find Interface Board
Clock Data Stuck
Board connected correct port, SMBus functioning
Address Acknowledged
SMBus response expected SMBus address
Conflict with local printer driver Erratic Operation Operating system conflict
Two-Wire Interface Board Evaluates: MAXSMBus
Table DB25 Connector Signals
18-25 NAME SPARE OUTPUT SMBCLK_ SMBDATA_ SMBUS_OUT LOOPBACK MASK_ ALERT1 MASK_ ALERT2 MASK_ START CAPTURE_ENABLE SMBDATA_ SMBCLK_ LOOPBACK SPARE OUTPUT HOLDING_ CLOCK UNUSED UNUSED Spare output When high, drives SMBCLK signal When high, drives SMBDATA signal When high, drives SMBSUS signal Loopback connection port verification When high, allows ALERT1 trigger When high, allows ALERT2 trigger When high, allows start condition trigger When high, enables slave monitor circuitry. This circuit waits until SMBCLK pulled low, then holds SMBCLK until software resets Active interrupt input When high, indicates that SMBDATA When high, indicates that SMBCLK Loopback connection port verification Spare output When low, indicates that interface board holding SMBCLK used used Signal ground return FUNCTION
Two-Wire Interface Board Evaluates: MAXSMBus
Table Right-Angle Header Signals
NAME DUTSMBSUS DUTSMBALERT DUTALERT2 SPARE OUTPUT SPARE OUTPUT POWER FUNCTION 20mA power supply Maxim companion board Signal ground return SMBDATA interface signal Signal ground return Signal ground return Signal ground return SMBCLK interface signal Signal ground return SMBSUS interface signal Signal ground return Primary ALERT interface signal Signal ground return Secondary ALERT interface signal Signal ground return Spare output from DB25 connector Signal ground return Spare output from DB25 connector Signal ground return Signal ground return Unregulated, unprotected power-supply input MAXSMBus interface board
Note: Odd-numbered pins outer row. Even-numbered pins inner row. right-angle header signals pass through MAX367 circuit protector, except
ALERT1 74HC04 J1-6 MASK_ALERT1 74HC05 ALERT2 74HC04 74HC08 74HC05 74HC05 START DETECTED 74HC74 4.7k 74HC04 SMBSUS SMBSUS J1-8 MASK_START 74HC08 START_DETECTED J1-10 J1-7 MASK_ALERT2 ALERT2 74HC08 ALERT2 ALERT1 ALERT1
Figure MAXSMBus Schematic
INTERFACE TEST POINTS HOLDING_CLOCK J2-1 SMBCLK_OUT J2-2 SMBDATA_OUT J2-3 SMBSUS_OUT J2-4 J2-5 J2-6 J2-7 SMBCLK_IN 74HC74 74HC05 74HC04 74HC05 74HC04 SMBDATA SMBDATA SMBDATA SMBCLK J1-18 J1-19 J1-20 J1-21 J1-22 J1-5 LOOPBACK J1-13 SMBCLK 0.1µF 0.1µF 0.1µF CAPTURE_ENABLE 74HC08 GRAB_SCL 74HC04 DRIVE_SCL_LOW CAPTURE_ENABLE 74HC05 SMBCLK DECOUPLING CAP. HOLDING_ CLOCK J1-15 J2-8 J2-9 J2-10 J2-11 J2-12 MASK_ALERT1 MASK_ALERT2 MASK_START CAPTURE_ENABLE SMBDATA_IN SMBCLK_IN 4.7k J1-23 J1-24 J1-25
SMBDATA_IN
SMBCLK
CAPTURE_ENABLE
SMBSUS_DUT J1-4
J1-9
CAPTURE_ENABLE
SMBCLK_OUT
J1-2
4.7k
J1-12
SMBCLK_IN
SMBDATA_OUT
J1-3
4.7k
Evaluates: MAXSMBus
J1-11
SMBDATA_IN
Two-Wire Interface Board
Evaluates: MAXSMBus
POS5 +10V SBCLK1 6.8V SBSUS1 ALERT1 ALERT2 RIGHT ANGLE HEADER P1-1 P1-3 P1-5 SMBSUS SMBALERT ALERT2 SPARE OUTPUT J1-1 SPARE OUTPUT J1-14 4.3V -10V P1-7 P1-9 P1-11 P1-13 P1-15 P1-17 P1-19 J1-1 J1-14 P1-2 P1-4 P1-6 P1-8 P1-10 P1-12 P1-14 P1-16 P1-18 P1-20 GND0 MAX367 SMBDATA SMBCLK SMBSUS ALERT1 ALERT2 SBDAT1
Two-Wire Interface Board
Figure MAXSMBus Schematic (continued)
POS9 LM78L05ACM 3.3µF 3.3µF 3.3µF C1V+ MAX865 +10V 3.3µF 3.3µF N.C. N.C. GND1 3.3µF -10V
Two-Wire Interface Board Evaluates: MAXSMBus
1.0"
1.0"
Figure MAXSMBus Component Placement Guide
Figure MAXSMBus Board Layout-Component Side
Two-Wire Interface Board Evaluates: MAXSMBus
1.0"
Figure MAXSMBus Board Layout-Solder Side
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 1998 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

Two-Wire Interface Board MAXSMBus interface between IBM-compatibl

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