pete at dunnington.plus.com
Fri Mar 31 01:21:48 CST 2006
On Mar 31 2006, 18:16, Ethan Dicks wrote:
> Yes... the lowest trap vectors on _all_ PDP-11s are fixed and mean
> something special when you hit them. I don't have a reference right
> in front of me (should be in all of the small computer handbooks),
> on a different spot on that page, it mentions this...
> Location Contents Opcode Comment
> 000004 000006 Bus Error trap
> 000006 000000 halt
> 000010 000012 Reserved
> 000012 000000 halt
> 000024 000026 Power fail trap
> 000026 000000 halt
> ... so if you really are halting at 000004, sounds like a bus error.
> Perhaps the code you toggled in can't find an I/O register it's
No, if you have set up the standard trap catcher, and you halt at 4, it
loaded the vector from 0, executed the HALT instruction at 2, and the
PC contains 4 by the time it stops or returns to ODT.
Pete Peter Turnbull
University of York
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