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-~
pins 32, 85, 86, and 87
-LOW signals should be observed on the following motherboard
pins:
\
s 29, 30, 31, 33, 34, 37, 79, 80, 81, 83,
84
11.
PRDY
should have execu
a si
1
struct
(JMP
gone into a wait state duri
instruction
address.
The Theory of
ration sect
n
s the auto-jump sequence.
If 5Ml
s h
h but
is wrong, check the data paths
r
h
POJ
multiplexors.
If 5Ml is LOW, sk
to
next
see if the processor can execute
tructions at
5Ml has an AC signal, check
wa t 1
ic from
WAI
C4.
-I
-~hi~ ste~
checks out the Z80A while executing a one
Ins~ructlon
program.
A. With\ the power off, remove the jumper -from PRDY to ground
from the ZPB.
B.-Turn~on the power and then depress and
release the reset
swit h.
The Z80 should be executing an RST 7 instruction
repe tedly.
Observe that all the data input (DI) lines are
HIGH by checking the following motherboard pins:
-p~ns
41, 42, 43, 91, 93, 94, and 95
C.
If you have an oscilloscope, then check that the signals
ZD0-~D7
are HIGH during Ml at the Z80A chip pins:
-p~ns
14,
15,
12, 8, 7, 9, 10, and
13
D. C~eck\ that the following motherboard address lines are AC
slgna~s:
-pips 29-34, 37, and 79-87.
"
E. The RST 7 instruction causes a subrouilne call to location
0038 hex, thus the stack address stored will be 0039 hex
(stored as alternating 00 byte and 39 hex byte).
Thus, if
you h ve an oscilloscope, observing the data output bus
(DO), the following motherboard bus pins should have AC
signa s that go low twice every 2.75 microseconds:
35, 40,
88,
and 90.
17
-and th\:
Signalr
pin~
following motherboard bus pins should have AC
that go low once every
2.75
microseconds:
36, 38, 39 -and 89
North Star Z80A PROCESSOR BOARD
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