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Chapter 2 -Basic Component Set-up
27
Figure 2-8
What the Diagnostic LEDs Mean
The Memory Board LEDs
888
<:=Test Number or Type of
Error~
Heartbeat
Exception Class Error
Failure
1.
If the LED in bit position 7 lights up during self-test, it indicates a failure.
The exact test that failed is indicated by LEDs 0 through 4, which can be
decoded by the "Diagnostic LEDs'' table shown previously.
2.
If the LED in bit position 6 lights up during the self-test, it indicates the
failure is an exception class failure -
bus error trap, address error trap,
unexpected interrupt, etc.
3.
LED 5 is the heartbeat LED. It will start blinking after the conclusion of
self-test and before the execution of
UNIX
to indicate that the CPU is actually
executing code and not hung somewhere.
4.
LEDs 0-4 indicate the exact test being undertaken during self-test. IfLED 7
is not lit, then the tests are proceeding without error; if LED 7 lights up,
then LEDs 0-4 will freeze, indicating which test failed. Refer to the previous
table, if necessary.
If all 8 LEDs are lighting up in sequence from 0 to 7 then back to 0 again, it
means that you have exited self-test and UNIX is running successfully.
Once you have exited self-test and UNIX is running successfully, only the green
LEDs should be lighted if the memory board is operating properly.
The table that follows will give you an idea of what each of the five LEDs on the
back of the memory board are for. In general, the green LEDs are lighted and all
others are off during normal operation. If one or more yellow or red LEDs light,
an abnormal condition exists. Or, if the green, refresh LED (the LED located at the
bottom) is off, the refresh circuitry is failing, and the board needs immediate
attention.
Revision A of 10 October 1986
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