Stockly.com Forums

Stockly.com Forums (http://www.stockly.com/forums/index.php)
-   Altair 8800 (http://www.stockly.com/forums/forumdisplay.php?f=15)
-   -   Emulator Status LEDs (http://www.stockly.com/forums/showthread.php?t=842)

rfeecs 09-02-2009 08:09 PM

Emulator Status LEDs
 
I was playing with Rich Cini's Altair32 emulator and noticed that the status LEDs change when I single step. According to the theory of operations manual, the Altair stops and steps only at instruction fetch cycles. So the status LEDs should always be the same after a step, reflecting the status for an instruction fetch: MEMR is on, M1 is on, WO is on.

This video shows this behavior: http://www.youtube.com/watch?v=vAhp_LzvSWk

It looks like the emulator doesn't handle the status LEDs correctly.

Anyone with a working Altair care to confirm this?

Geoff Harrison 09-03-2009 04:37 PM

Quote:

Originally Posted by rfeecs (Post 1918)
I was playing with Rich Cini's Altair32 emulator and noticed that the status LEDs change when I single step.
...
Anyone with a working Altair care to confirm this?

Yes, you're right. A real 8800 will step one full instruction at a time whereas Rich's emulator steps one byte at a time. There are a few differences (bugs?) in the emulator, but that doesn't detract from how useful it is for developing programs for the Altair.

Geoff.

rfeecs 09-03-2009 05:55 PM

That explains it.

Actually, from the point of view of understanding how the 8080 CPU works and looking at the status lines, stepping one machine cycle at a time is better.

I agree the emulator is a great tool. It's also great that he's collected so much of the original software ready to run on an Altair into one package.


All times are GMT. The time now is 02:36 PM.

Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.