Agilent Technologies 4284A Service Manual page 160

4-21 . A40 SCANNER I NTERFACE (OPT.301 ) SERVICE S HEET
4-2 1 - 1 . CIRCUIT DESCRI PTION
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-cou plers A40U3, A40U4, A40U 5 ,
a n d A40U6. The pull-up resistors for the input signals are selected u s i n g jumpe rs A40SW1
and A40SW2.
[ EEPROMs ]
E E P R O M s A40U7 and A40U 1 2 ( 64 KBytes ) are used to store compensation data for 1 28
channels.
[ Peripheral Interface Adapter ]
Peripheral interface adapter ( A40 U9 ) interfaces between the A7 C P U board and the 40
board.
4-21 -2. TROUBLESHOOTING AIDS
The test pOints are listed in Table 4-A40-1 .
Test Point Signal Name
A40TP 1
A40TP2
COAlMON
A40TP3
A40TP4
A40TP5
C
.
Table 4-A40-1 . Test Points
Description
External trigger signal
EXT TRIC
LrT DCV
External DC voltage
Common line
VCC
+5 V DC
ND
Ground line
4-A40-1