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8842A
Instruction Manual
6-46
programmed as inputs to prevent contentions between them and the outputs from other
ICs which drive them. Data coming into all µC inputs (except pin 38) is ignored.
NOTE
If the A/D IC (U101) is working properly, its watchdog timer briefly
interrupts all of the In-Guard Troubleshooting Mode signals every 1.5 sec
for a period of about 0.2 sec. (The signals are then re-established.) If this
occurs, the main counter in U101 and its watchdog timer are operating
correctly. (See step 6, below.)
When the test is complete, turn off the 8842A and remove the short from TP205.
6-42. In-Guard Microcomputer
While the 8842A is in the In-Guard Troubleshooting Mode, check the following in the
order shown:
f6-09.wmf
Figure 6-9. U202 Pin Diagram