Latest additions to 680 project

[Chris Davis]

https://youtu.be/cGlpKO8zOKY

Here's whats new with my 680.

[Tom Wilson]

Chris, is the Altair 680 Due emulator up on Github, yet? 

I'm thinking of working on a series of "old time" assemblers, which would be optimized for front panel data entry (but also put put out binary files, Intel Hex, and Motorola Hex files.)

I'd love to have the 680 emulator to start messing with and maybe create some sample code, since there's not nearly as much Motorola 6800 content out there as there is for Z80 and 6502.

[Charley Jones]

Great work guys. 

Weened my teeth on 6800 and Z80.

Can’t wait to build one 

Sent from my iPhone 15pm!

Charley Jones, PMP

On Aug 19, 2025, at 7:40 PM, Tom Wilson <wils...@gmail.com> wrote:

Chris, is the Altair 680 Due emulator up on Github, yet? 

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[Tom Wilson]

Never mind. I found the repository.

Thank you, Chris, for such excellent work. I have ordered another Due board, so I'll be able to start testing this soon.

I've also started laying out my assembler. It's amusing how similar this is to MOS 6502... it's almost like the MOS guys started at Motorola, or something. 

[Phillip Harbison]

Tom Wilson wrote:
> Never mind. I found the repository.

Link?

> I've also started laying out my assembler. It's amusing how similar this
> is to MOS 6502... it's almost like the MOS guys started at Motorola, or
> something.

Perhaps because they did? ;)

I wrote tons of 6502 assembler mostly for custom industrial control. I
never used the 6800 but did some work with the 68000 family, the 6809,
and the 68120. The latter was derived from the 6801 and featured a 128
byte dual port RAM accessible by an external processor. It made a great
I/O processor. I used it as such in a cable TV studio automation system.
My design was based in part on this application note.

http://www.bitsavers.org/components/motorola/_appNotes/AN-0850_Multi-Processor_Controller_Using_The_MC6809E_And_The_MC68120.pdf

https://datasheet4u.com/pdf-down/M/C/6/MC68120-Motorola.pdf

Is there any plan to do any Arduino-based 6809 replica? I ported QC, a
Z80 C compiler, to the 6809 and would like to play with it again.

--
Phil Harbison

[Tom Wilson]

Phil, https://github.com/davischris/AltairDuino680

Yes, the 6502 story is very similar to the Z80 story. The guys who started MOS worked at Motorola and wanted to build a low-cost desktop CPU. Motorola wasn't interested in that at the time, so the MOS founders went off and made history.

The 6800 and 6502 are similar, but not identical. I guess there were some legal threats involved... There are some different instructions, and the mnemonics are pretty different. Regardless, I'm hoping to build my assembler so that you can simply plug in different language packages and switch to 6502 or 8080 using the same basic framework.

[Phillip Harbison]

Tom Wilson wrote:
> Phil, https://github.com/davischris/AltairDuino680

Thanks!

> The 6800 and 6502 are similar, but not identical. [...]
The index registers, indirect addressing, and zero page were a nice
addition. From 01/1979-04/1981 I worked for Cybersystems, a Huntsville
company that had a line of modules based on the 6502. The boards were
the same size as STD bus (6.5" x 4.5") but the connector had 64 pins on
0.1" centers vs. 56 on 0.125" and control signals compatible with 6800
and 6502 vs. 8080/Z80. Most of the modules were I/O-oriented such as
ADC, DAC, and relay drivers. We would build custom industrial control
systems using those modules.

We were working on a desktop system much like the Kaypro but with a
built-in dot matrix printer and our cared cage in the back. We used a
Z80 to run CP/M but all I/O except the display was handled by a 6502.
They never brought it to market. I left shortly after graduating from
UAH in 1981 (BSEE).

My favorite 8-bit processor was the 6809 but once I started working with
the 68000 family I never really looked back. After years of swimming in
oceans of 6502 and Z80 assembly code I did not want to touch anything
that could not easily support C. I wrote just enough 68K assembler to
initialize the CPU, handle interrupts, and call the C code. ;)

--
Phil Harbison

[Tom Wilson]

Not the 680, but obviously related:

https://youtu.be/OsikuBXmJIo?si=zlNp2xqSBnU49HwS