A 4 0 Scanner Interface (Opt.301) Service Sheet 4 - A - Agilent Technologies 4284A Service Manual

4-21. A40 SCANNER INTERFACE (OPT.301) SERVICE SHEET
4-21-1. CIRCUIT DESCRIPTION
The A40 scanner interface board consists of photo couplers, EEPROMs, Static RAMs, and a
peripheral interface adapter ( PIA ).
[ Photo Couplers ]
When the scanner interface connector on the rear panel is used to synchronize an external
scanner, the input/output signals are opto-isolated by opto-couplers A40U3, A40U4, A40U5,
and A40U6. T h e pull-up resistors for the input signals are selected using jumpers A40SW1
and A40SW2.
[ EEPROMs ]
EEPROMs A40U7 and A40U12 ( 64 KBytes ) are used to store compensation data for 128
channels.
[ Peripheral Interface Adapter ]
Peripheral interface adapter ( A40U9 ) interfaces between the A7 CPU board and the 4 0
board.
4-21-2. TROUBLESHOOTING AIDS
The test points are listed in Table 4-A40-1.
Test Point Signal Name
A4OTP1
EXT_TRIG
A4OTP2 E X T___DC V
A4OTP3
COAIMON
A4OTP4 VCC
A4OTP5 GND
Table 4-A40-1. Test Points
Description
External trigger signal
External DC voltage
Common line
+5 V DC
Ground line
4-A40-1
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