Peter I presume by ODT you mean the 11/23 Console ODT, there are ODT programs from the Paper Tape era which can be useful on bare metal. ODT's cousin DDT and family tree are sketched in https://en.wikipedia.org/wiki/Dynamic_Debugging_Technique
If you wish a full fat ODT for bare metal, albeit expecting paper tape input (octets into the console terminal should serve), you could investigate DEC-11-XPTSA-B-O Paper tape Software handbook - section 5.3.4 pg 5-12 pdf pg 114 :: is a good starting point, the "tapes" you wish are ODT-11 and ODT11-X. Given the Halt + Proceed incantation, only the later / larger / more comprehensive ODT11-X has an instruction step capability. The DEC hardware mechanism for single step and breakpoints, is a combination of the Trace Trap bit in the PSW, its chum the TRAP OpCode, and as illustrated by Halt + P : microcode. I would leave interfacing with that to paper tape ODT or a more recent debugger; their greatest utility is to increase the size of the key hole you peer through (into the program / machine) Martin -----Original Message----- From: Jos Fries via cctalk [mailto:[email protected]] Sent: 01 November 2025 16:38 To: [email protected] Cc: Jos Fries <[email protected]> Subject: [cctalk] Re: Looking for a bootloader 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. >>> [...] >>
