Model
8901B
Service
a
CPU
External Register (RAM) Check
1.
Perform the Power-Up Chechs on Service Sheet BDI.
aCPU
1/0
Port Check
1.
If the Digital Test/Extender Llonrd is not already extcriding
A12
or
A13,
plug
it
into
the empty
slot
in the Digital Section.
NOTE
2.
Key
in
0.2
SPCL. Check the
INSTRUMENT
BUS
test
points
on
the extender- board
wit11
an
oscilloscope
or
signature analyzer probe (used
as
n
logic probe)
as
listed
in
Table
8D--17.
If
faulty, see Service Sheet 24 and check the
CPU
and
li0
port decoders and buffers.
Tuble
80-1 7.
Insfririncwi
Jlrir
Ihifu,
=Sfup
2
3.
Key
in
0.2
S
(Shift)
5
S
5
SPCL.
Recheck the test points listed
in
Table 8D-18.
If
faulty, see
Service Sheet 24
and
check the
CPU
and
1/0
port decoders
and
buffers.
Table
80-
18.
Inslriimcnf
Biis
Ilczia,
aSicp
3
DATA
(H)
0
to
3
TTL
High
4. Key
in
the Special Functions listed in
Tablc
8D-19.
For
each entry.
the
indicated
ENABLE
test
point on the estender board
shoiild
show
low-going
TTL
piilses with
;1
period of approximately
60
nis.
All
other
ENABLE
test points should be
TlL
highs.
If
Ihiilty, see Service Sheet 24 and
check the Enable Decoder
and
CPU.
I
SDecial Function
1
Test
Point
~
I
0.0
0.1
0.3
0.4
0.5
0.6
0.7
ENABLE
0
ENABLE
1
ENABLE
3
ENABLE
4
ENABLE
5
ENABLE
6
ENABLE
7
8D-58
Service Sheet
BD5
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