GPlB
ADDRESS
S
ITCH
AND
BUFFER
TEST
GPlB
address switch
S1221
I.
Purpose
Check operation of GPlB buffer and address switch.
II.
Equipment required
A.
Oscilloscope
B. TM
500 Flexible Extenders, Tektronix Part Number 067-0645-02
C. Voltmeter
Ill. Electrical conditions necessary to perform test
A.
Check U1212 pin 20 for
+5
V
B.
Check U1212 pin 14 with oscilloscope for approximately a 1
MHz
signal.
C.
Set J1220
as
shown.
IV.
Setup (PS 5010)
A.
Remove CPU U1111 (to free up data bus).
B.
Remove R1211 (to open data bus).
V.
Measurements
Using oscilloscope connected to U1212 as shown and checking for highs and lows, exercise GPlB
address switch and mode jumper (J1320). Check for stuck, shorted or open signal paths. If problems
are found trace to buffer, switch, pull-up resistors or circuit board.
Depress this
side
=
low
-)
Depress this
side
=
high
-f)
0
08
0
0
1
1
-
DDDDDD
012345
Mode
jumper
5
1320
m
nc
131
06
(Short
to
ground for low;
open for high)
07
(Short
to
ground
for
low;
open for
high)
I I
CPU
board
Fig.
9-
1.
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