4 Nov
2025
4 Nov
'25
8:03 a.m.
Hi Jos,
Thank you for pointing this out. I feel I should have known that. :) I must
have glossed over that when I was looking through the manuals.
- Peter
On Sat, Nov 1, 2025 at 2:28 PM Jos Fries via cctalk <cctalk(a)classiccmp.org>
wrote:
Peter,
Single-stepping a PDP-11/23 is done by putting the HALT switch in the down
(Halt) position and then issuing the Proceed or Go command. See the KDF11-A
User’s Guide par. 3.4.7.
Jos
Op 1 nov 2025 om 13:58 heeft Peter Ekstrom via
cctalk <
cctalk(a)classiccmp.org> het volgende geschreven:
Hi Jay,
Thank you for this information! I didn't think of trying that. Paul's
suggestion to set PSW to 340 and a reset works as well.
But it is good to have more options. :) Now to figure out why it won't
run
on my hardware 11/23. Is there a stand-alone
debugger for bare metal stuff? I'd like to be able to single-step but ODT
doesn't have that ability. Got spoiled by SIMH.
- Peter
> On Sat, Nov 1, 2025 at 7:23 AM Jay Logue via cctalk <
cctalk(a)classiccmp.org>
> wrote:
>
> Classic stray LTC interrupt. You can disable LTC interrupts in simh by
> setting the NOBEVENT option (11/23 and 11/03 only). This simulates
> disabling the LTC via the front panel switch or a jumper on the CPU
> board. E.g.:
>
> $ pdp11
> PDP-11 simulator V4.0-0 Current git commit id: 5cfa8662
> sim> SET CPU 11/23
> sim> SET CPU 32K
> sim> SET NOBEVENT
> sim> RESET
> sim> load loop.bin
> sim> g 14000
> ^E
>
> Simulation stopped, PC: 014006 (BR 14004)
>
> Note that a RESET is need after NOBEVENT is set in order for it to take
> effect. This is because the NOBEVENT option effectively changes the
> default value of the Interrupt Enable bit in the LTC control register
> upon a system reset.
>
> --Jay
>
>> On 10/30/25 07:39, Peter Ekstrom via cctalk wrote:
>> Anyone here familiar with programming the 11/23 (KDF11-A) in assembler,
>> bare metal?
>> I have been trying to get a very simple test program to run on it but
it
>> keeps halting on
>> an address outside of the program. Seems to always be the same address
>> which is why
>> I am thinking I must be missing something. The program runs fine on an
>> 11/23+ or 11/70.
>> [...]
>