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 <[email protected]> > 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 <[email protected]> >> 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. >>> [...] >>
