Electronics > FPGA

Replicating a 'custom' 6800 in FPGA

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bingo600:
I just assembled the source code with as11 , no issue at all.

https://github.com/JimInCA/motorola-6800-assembler


--- Code: ---./as11 S00060G.asm -l >S00060G-11.lst

--- End code ---


If you are "lucky" (HC11 ressources) you might be able to use the HC11 as Timer and PIA

Nice HC11 site
http://www.hc11.demon.nl/thrsim11/68hc11/


metertech58761:
Really?! That version compiled with no hiccups?! Cool! (considering I did NOT use a standard assembler to make that version)

That would be awesome if I could combine the PIA and PTM into the HC11...
All three timers in the PTM are used (one is used as an internal programmable delay, the second drives the _NMI line, and the third is XOR'd with the outgoing data stream).

I know of a board that was part of this system that probably did just that, but I have not been able to track down the particulars of the HC11 that was used in that role.
I'm guessing it too was a custom variant (it was a 68-pin PLCC whereas pretty much all the remaining HC11s available are 52-pin PLCC).

Anyway, I want to see if I understand correctly how to connect the HC11 in 'expanded' mode - here's a schematic I worked out for an "adapter".

bingo600:
Remember ... That it assembles the source , doesn't mean it will work w. the HC11 internal timers etc.
You would need to "decode" the timer & PIA usage , and replicate that w. HC11 "internals"
I even think it created a 100% equal .bin file  HC11 vs "Original bin"

This one might come in handy to understand the Timer ... The DS is a bit cryptic i think.
http://www.bitsavers.org/components/motorola/_dataSheets/MC6840UM.pdf

I'm not an EE , just a hobby'ist.
The electrical design should be reviwed by someone else.

Good info
https://mil.ufl.edu/3744/software_hc11.html


HW Inspiration
https://inworks.ucdenver.edu/jkb/legorobots/hardware.html


Mux'ed
https://www.kswichit.com/C11evb/C11evb.htm


https://hackaday.io/project/171451-68hc11-cpu-board-for-rc2014
https://cdn.hackaday.io/files/1714517335359584/68hc11.pdf

Non mux'ed
https://www.cs.uml.edu/~fredm/handyboard.com/oldhb/schemv12/hbsch12.pdf
https://mil.ufl.edu/3744/docs/11EVBU-SCH-D.pdf




Edit: You do know the HC573 is a 373 with a much nicer pin layout

/Bingo

SiliconWizard:

--- Quote from: bingo600 on September 29, 2021, 05:23:36 am ---Remember ... That it assembles the source , doesn't mean it will work w. the HC11 internal timers etc.

--- End quote ---

Quite right of course. And with that said, although the CPU the OP is trying to replace supports the 6801 instruction set, nothing tells us that it acts as one either - be it for cycle-accuracy, interrupts, and so on...

bingo600:
If clocked by 1MHz as the 01' , and given that the Binaries were "equal" i'd expect the normal instructions to execute 1:1
IRQ could push a bit more or less , but that's prob. not an issue.


/Bingo

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