Stockly.com Forums  

Go Back   Stockly.com Forums > Altair 8800 > Altair 8800

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 09-02-2009, 08:09 PM
rfeecs rfeecs is offline
Junior Member
 
Join Date: Feb 2008
Posts: 6
Default 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?
Reply With Quote
  #2  
Old 09-03-2009, 04:37 PM
Geoff Harrison Geoff Harrison is offline
Senior Member
 
Join Date: Feb 2007
Posts: 104
Default

Quote:
Originally Posted by rfeecs View Post
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.
Reply With Quote
  #3  
Old 09-03-2009, 05:55 PM
rfeecs rfeecs is offline
Junior Member
 
Join Date: Feb 2008
Posts: 6
Default

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.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Front Panel LEDs and Other Issues TomL_12953 Troubleshooting 4 08-20-2009 01:43 AM
Altair kit up and running. Geoff Harrison Altair 8800 28 02-22-2009 02:28 PM


All times are GMT. The time now is 01:45 PM.


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