SIMH simulators I have used have tracing. Looks like Altair doesn't but AltairZ80 does. ./altairz80 sim> set cpu history=2000 sim> step 100 Step expired, PC: 00064 (NOP) sim> show history CPU: C0Z0M0E0I0 A=00 B=0000 D=0000 H=0000 S=0000 P=0000 NOP CPU: C0Z0M0E0I0 A=00 B=0000 D=0000 H=0000 S=0000 P=0001 NOP CPU: C0Z0M0E0I0 A=00 B=0000 D=0000 H=0000 S=0000 P=0002 NOP CPU: C0Z0M0E0I0 A=00 B=0000 D=0000 H=0000 S=0000 P=0003 NOP ... To save to file show @file history output will be in FILE On Fri, May 15, 2026 at 11:51:08AM +0000, Richard Cini via vcf-midatlantic wrote:
Thanks Ken. I just tried that and it doesn’t help. I set a breakpoint at the command found address and typed a valid command name and it never reaches it. So, it has to be around where you’re looking. I’ve been using SIMH which is not great IMHO for tracing so I’m going to see if I can run this in another emulator with a debugger.
Rich
-- Rich Cini http://cini.classiccmp.org https://github.com/RichCini
From: Kenneth Gober <kgober@gmail.com> Date: Friday, May 15, 2026 at 12:52 AM To: vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> Cc: Richard Cini <rich.cini@gmail.com> Subject: Re: [vcf-midatlantic] 8080 monitor command line processor help needed
On Thu, May 14, 2026 at 9:15 PM Richard Cini via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org<mailto:vcf-midatlantic@lists.vcfed.org>> wrote: POP D ; Restore table pointer POP H ; Restore input pointer
; Move to next table entry LXI H,CMD_LEN + 2 ; Size of entry (string + address) DAD D XCHG
I think the "POP H" needs to be moved after "XCHG". otherwise LXI H obliterates it and you lose track of the input pointer.
-ken