HP Integral Personal Computer Service Manual page 143

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.