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8·80 Troubl •• hoot'ntI and D'.gnostlc.
1m ......
".,eon ••
Colllpute,
Tabl. 8·24. Troubl •• hooting DTACK and Interrupt Probl ..... (Continued)
UIG
Input Pins
UIG
Output
Pins
Int_rupt
Level
4
3
2
1
L
X
X
X
H
L
X
X
H
H
L
X
H
H
H
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
13
12
X
X
X
X
X
X
X
X
L
X
H
L
H
H
H
H
Step
11
X
X
X
X
X
X
L
H
•
L
L
L
L
H
H
H
H
1. Set up the computer to troubleshoot the
logic A PCA (refer to table 8-27). Determine
the logic states of the U60 input and output
pins with a logic probe. Compare the input
and output with the above table.
2. Take the action indicated for the specific er-
ror message below:
***
ERROR - INTERRUPT LEVEL 1
occurred when
it
should
not
have.
***
ERROR - REAL TIME CLOCK
interrupt error.
***
ERROR - INTERRUPT LEVEL
n
occurred when it should
not
have.
Where
n
==
2
or 7.
***
ERROR - INTERRUPT LEVEL
n
occurred when it should
not
have.
Where
n
=-
3
through 6.
***
ERROR - Disc interrupt
error.
I
7
L
L
H
H
L
L
H
H
8
L
H
L
H
L
H
L
H
7
6
5
4
3
2
1
No Interrupt
Indicated Action
If
the output-pin states do not correspond cor-
rectly to the input-pin states, replace U60.
If the output-pin states do correspond correctly
to the input-pin states, go on to step 2.
Substitute a known-good logic B PCA; replace if
necessary.
If
the problem persists, replace the
logic
A
PCA.
Substitute a known-good. logic B PCA; replace if
necessary. If the problem persists, replace the
lOgiC A PCA.
Substitute a known-good keyboard; replace if
necessary. If the problem persists, replace the
logic A PCA.
Remove, one at a time, any peripherals and
in-
terfaces that are connected to the computer.
Repeat the test after each removal.
• If the problem is corrected, troublesboot the
defective device.
• If the problem persists, substitute a known-
good logic B PC A; replace if necessary.
If
the
problem persists, disconnect the
I/O
backplane PCA. If this corrects the problem,
replace the
I/O
backplane PCA; otherwise,
replace the logic A PCA.
Substitute a known-good logic B PC A; replace if
necessary.
If
the problem persists, replace the
logic A PCA.
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