Tough to Diagnose issue with PDP 11/40 CPU

[william degnan]

I thought I'd throw this one out to those who know more than I about the
PDP 11/40
I am working with DaveR on vcfed.org/forum who asked me to run the
following program as a test from the front panel:

20 - 220 ; IOT trap vector (New PC)
22 - 340 ; IOT trap vector (New PSW)

200 - 012706 ; MOV #600,SP
202 - 600
204 - 240 ; NOP
206 - 0 ; HALT
210 - 4 ; IOT
212 - 240 ; NOP
214 - 0 ; HALT
216 - 0 ; HALT
220 - 0 ; HALT
222 - 0 ; HALT

START the program running from address 200.

----------------------

Problem is - The IOT step is bombing (?) and loops through the addresses:
204
206
210
200
204
206
210
200
endlessly.

Anyone care to speculate which CPU card is the culprit?


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