Digital circuitry checks
Digital circuit problems can be checked out using Table 4-3. See principles of operation for
a digital circuit description.
Table 4-3
Digital circuitry checks
Step Item/component Required condition Remarks
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Power-on test
U3, pin 19, TP3
U3, pin 7, TP1
U3, pin 68, TP10
U3, lines A0-A19
U3, lines D0-D15
U3, pin 66, W23
U4, pin 7
U4, pin 8
U13, pins 34-42
U13, pins 26-31
U13, pin 24
U13, pin 25
U3, pin 43
U3, pin 44
U3, pin 45
U3, pin 47
RAM OK, ROM OK.
Digital common.
+5V
Low on power-up, then goes
hi
gh.
C
heck for stuck bits.
Check for stuck bits.
16.78MHz.
Pulse train during RS-232 I/O.
Pulse train during RS-232 I/O.
Pulse train during IEEE-488 I/O.
Pulses during IEEE-488 I/O.
Low with remote enabled.
Low during interface clear.
Pulse train.
Pulse train.
Pulse train.
Pulse train.
Verify that RAM and ROM are
f
un
ctional.
All signals referenced to digital
commo
n.
Digital logic supply.
MPU RESET line.
MPU address bus.
MPU data bus.
MPU clock.
RS-232 RX line.
RS-232 TX line.
IEEE-488 data bus.
IEEE-488 command lines.
IEEE-488 REN line.
IEEE-488 IFC line.
D_ADDATA
D_DATA
D_CLK
D_STB
Troubleshooting 4-15
2410-902-01.book Page 15 Monday, November 7, 2005 2:49 PM
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