Service manual

Appendix A
Console Error Messages for Model 300
Table A–1 lists messages ?02 through ?1F which appear when the processor
halts and the console gains control. Each message is followed by a "PC =
xxxxxxxx" message giving the address where the processor was executing
when it halted; these messages designate the reasons for the halt.
Table A–2 lists the standard console error messages ?20 through ?7C.
Table A–1: Model 300 Console Error Messages Indicating Halt
Error Message Meaning
?02 External halt.
CTRL-P
or STOP command.
?04 Interrupt stack not valid. Interrupt stack pointer contained an in-
valid address.
?05 Machine check during exception. A machine check occurred while han-
dling another error condition.
?06 Halt instruction executed. The CPU executed a Halt instruc-
tion.
?07 SCB vector bits <1:0> = 11. An interrupt or exception vector in the
System Control Block contained an in-
valid address.
?08 SCB vector bits <1:0> = 10. An interrupt or exception vector in the
System Control Block contained an in-
valid address.
?0A CHMx executed while on interrupt stack. A change-mode instruction was issued
while executing on the interrupt stack.
?0B CHMx to interrupt stack. The System Control Block vector for a
change-mode instruction indicated ser-
vice on the interrupt stack.
?0C SCB read error. The System Control Block was not acces-
sible in memory.
?10 ACV or TNV during machine check. An access violation or translation-not-
valid error occurred while handling an-
other error condition.
Console Error Messages for Model 300 A–1