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.
[...]
