21 Jul
2010
21 Jul
'10
7:08 p.m.
On 7/21/10 3:03 PM, Bill Sudbrink wrote:
Um, no. You don't understand how the front panel of the IMSAI
works.
Actually yes I do. :) I've had to dig into it several times over the
years.
I was reading something the other day about being able
to hand-clock a
Z80, that it was so stable (due to not using dynamic registers,
apparently) that with the appropriate debounce circuit you could literally
manually step it through instructions.
Is this as rare as it sounds?
Has anyone -tried- hand-clocking a Z80?
Umm yes, it's called single-stepping, and it's very common. The first
Z80 system I had that had support for that built-in was my IMSAI 8080.
I used single-stepping to debug my BIOS modifications in the mid-1980s.
And yes my IMSAI "8080" is actually a Z80 system...It has a CCS 2810
CPU board which is compatible with the IMSAI front panel circuitry. :) It uses memory wait to stop the processor. It
doesn't
have anything to do with the CPU clock.
No, I didn't say it did, I was talking about single-stepping in
general in the context of the IMSAI system. It is indeed possible to
single-step a Z80 by manually pulsing the clock. One of my SBCs does
exactly that, based on a circuit in one of Steve Ciarcia's books.
-Dave
--
Dave McGuire
Port Charlotte, FL