Stockly.com Forums  

Go Back   Stockly.com Forums > Altair 680 > Altair 680

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 09-01-2007, 02:54 AM
joewing joewing is offline
Junior Member
 
Join Date: Sep 2007
Posts: 5
Default 6800 Details

Hello!
I've implemented an Altair 680 on a Spartan-3E FPGA, unfortunately
getting BASIC to load is giving me difficulties. I've found two versions
of BASIC online and tried both with little success. I think my problem is
the setting of the flag registers.
Anyway, I guess my question is, do the TBA and TAB instructions affect
the flag registers? Also, what is the proper behavior for CPX, ROR, ASR,
and LSR?

For a little background, I'm using a Spartan-3E starter kit attached
to a VT-320. I'm using 16k of RAM (which is loaded on reset with BASIC)
all implemented in the FPGA. If anyone's interested in the source (all
Verilog), I'd be more than happy to provide it.

Thanks!
Reply With Quote
  #2  
Old 09-01-2007, 03:00 AM
Grant Stockly Grant Stockly is offline
Administrator
 
Join Date: Jan 2005
Posts: 447
Default

Did you find this site from the S record header? One of the two versions probably came from me. I got the KCACR basic off of a real cassette tape. I've tested/verified two versions and released them out on the web.

I know this sounds stupid since you're obviously smart enough do the FPGA work... but have you been jumping to 0000? Are you sure your memory image is good? I can e-mail you mine.

Can you run the 6800 ACIA monitor? I can send you the binary file for that if you want.

Grant
Reply With Quote
  #3  
Old 09-01-2007, 03:08 AM
joewing joewing is offline
Junior Member
 
Join Date: Sep 2007
Posts: 5
Default

I found this site searching for information about the Altair 680 actually
One of the two versions of BASIC I'm using came from this site. It gets to
the point where displays the version info (and the RAM size, though
incorrectly) and then just does bizzare things.

The ACIA monitor runs perfectly... not sure where I found that...,
I'm actually tempted to try VTL-2, though I haven't found a S file for
that (I wrote a nice little C program to turn S files into Verilog).
I have a PDF document with the VTL-2 assembly listing in it, but typing
all that in would be painful.
Reply With Quote
  #4  
Old 09-02-2007, 02:51 AM
joewing joewing is offline
Junior Member
 
Join Date: Sep 2007
Posts: 5
Default

Here's a picture of it running, still fighting with this guy
It dies after the PRINT.

Reply With Quote
  #5  
Old 09-02-2007, 07:55 AM
Grant Stockly Grant Stockly is offline
Administrator
 
Join Date: Jan 2005
Posts: 447
Default

Thanks for keeping me updated! Are you using a public core or your own? Have you made a test series for it and verified all of the opcodes and status bits?

The next step should be a vga core to emulate a terminal. There is a GREAT project out there that I tried on my Spartan 3 kit. It is a complete System09 on the board. VGA, PS2, monitor, etc. If you want I can try to find the site.

It ran out of the box on the Digilent board.
Reply With Quote
  #6  
Old 09-03-2007, 03:48 AM
joewing joewing is offline
Junior Member
 
Join Date: Sep 2007
Posts: 5
Default

I'm using my own core. I've developed a fairly large test for it, though
there are still several instructions that need to be exercised more.
I got it to finally display the proper amount of free memory, though
it still doesn't want to work right... More testing
Of course the problem for a few things is that I don't know what the proper
behavior should be. The two 6800 instruction set listings I have been
using disagree on a few details:
ftp://ftp.comlab.ox.ac.uk/pub/Cards/txt/6800.txt
and
http://www.electronics.dit.ie/staff/...structions.htm

For example, one says CPX sets the carry flag, the other says it doesn't
(of course one also gives the same opcode for TAB and TBA).
Once I get everything working with the VT-320, PS/2 and VGA capabilities
certainly would be fun

Anyway, that System09 project looks pretty cool, I may have to load that
up and give it a try.
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
For sale: SWTPC 6800 systems (running) W0XEU Classifieds 3 09-07-2011 02:43 PM
For Sale - 6800 SWTPC systems W0XEU Classifieds 3 09-07-2011 02:41 PM
Altair 680 front panel operation sje Altair 680 6 02-04-2008 05:33 AM


All times are GMT. The time now is 10:56 AM.


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