Electronics > FPGA

Replicating a 'custom' 6800 in FPGA

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Regarding 'just because it compiles doesn't mean it will work', it turns out you are correct...

I had the opportunity to look through the source code I'm making and found one opcode I forgot to change. :)

Also, going back and taking a closer look at the main loop to better understand how it works actually revealed that one section of 15 bytes was accidentally repeated by whoever originally assembled this code (but, given the inefficiency of parts of the code I've since cleaned up, not terribly surprising).

Going back to post 76, I was hoping to verify that I understood how the R/W line is supposed to be derived when using the HC11, or if I am supposed to use the STRB/RW line directly.

Just a quick postscript before I start a couple new threads elsewhere.

In the end, I chose to use a 68HC11F1 (the 68-pin PLCC version).

For one, it has on-board RAM, which allows me to consolidate the two RAM ranges and eliminate the MC6810 and HM-6561 SRAMs once and for all.

The other is that it has the 6801 opcode set, so changes to the firmware should be limited to just relocating the upper RAM and I/O ranges.


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