6809 processor running on duodyne (not 6809E)

Hi, this weekend I built the duodyne 6809 (note: the original 6809, 68A09, and 68B09, not the MC6809E) processor board and it works great.

I am running MON09 ROM debug monitor. Dan designed and prototyped the board and seems to have hit the mark on the first try. He is busy porting Cubix to the new processor board. Soon we’ll have another processor on duodyne.

It can run 6809 single processor mode or as Z80/6809 multiple processor (not concurrent – switches back and forth but shares bus, memory, & IO). For those who like 6809, this is an interesting development.

duodyne is intended to be processor generic so the main processor can be either Z80 (default), 65816, TMS9995, or now the 6809. Z80 is the hardware path finder but as new processor boards come online, I expect it will soon be sharing the system with other processors. If people want to run something other than Z80 they now have a choice in even a single processor system. I prefer Z80 with RomWBW but whatever is your preference.


(6809 processor is board 23, near bottom of list of folders)

PS, one person is running a HD63C09P CPU if you’re into those. I haven’t gotten that far yet as I was thrilled to see my original 1 MHz MC6809P chip working after all these years although the 3 MHz HD63C09P is certainly tempting.

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Does anyone have a good document on the different variations of the 6809 from Moto? The reference to “not MC6809E” piqued my interest and the wiki article lacks an explanation.

The difference between MC6809 and MC6809E mostly comes down to the presence of the clock generator. The MC6809 is the earlier version which includes the clock generator on chip. The MC6809E is later version which does not include the clock generator and frees up the pins for other purposes. The two are not pin compatible.

I associate the MC6809E with the Tandy Coco and Dragon 64 type computers with MC6847 video chip. The MC6809E also contains some other extra features in software which improve its capabilities over the earlier MC6809 CPU.

Here is a good explanation on YouTube https://www.youtube.com/watch?v=VKfjEDQ0s9Q

Thanks, Andrew Lynch

Do you have any examples of these extra software features in the 6809E?

I understood the MC6809 and MC6809E used the same die and were just bonded out differently. So I would be surprised if there were any software differences.

My interest in this stems from he 6809/6309 Decoder I wrote recently. This is a debugging tools that reconstructs an full instruction trace together with the internal register state from a logic analyzer capture of the data bus and a few control lines.

If the 6809 and 6809E do behave differently from a software perspective, it looks like I might have more work to do.

I’ll watch the video you linked when I have a spare moment tomorrow…


Sorry, had that confused with 6309 not 6809E

Thanks, Andrew Lynch

Ah yes, that makes much more sense. I spend a fair amount of time in the decoder trying to understand both the documented and undocumented behaviours of the 6309. It really is a very interesting processor.