<tpb>
Title: GitHub - emeb/up5k_6502: A simple 6502 system built on a Lattice Ultra Plus 5k FPGA (at github.com)
<emeb>
I tweaked it slightly to use one of the SPRAM cores for the main system memory, so the 6502 has 32kB RAM and 4kB ROM in this build.
<tnt>
emeb: nice ! I'll try to give this a shot next week end :)
<tnt>
emeb: what target board did you use btw ?
<emeb>
tnt: I built it on a upduino I had laying around.
<emeb>
and I used my custom-made USB->SPI board to directly load the up5k so you'll definitely need to tweak the "make prog" target for whatever programming hardware you have.
<tnt>
I'll probably try on the icebreaker and use iceprog.
<emeb>
tnt: great - I was hoping someone would try it on that. I don't have one so I can't do it myself.
<emeb>
does icebreaker have a USB serial port hooked up to the FPGA?
<tnt>
yes it does.
<tnt>
the same ftdi that's used for programming has a 2nd interface configured as uart.
<emeb>
nice. so pretty much all you need to do is rearrange the pin assignments in the .pcf file to match the icebreaker I/O.
<emeb>
and revise the 'prog' target in the makefile.
<tnt>
I might try it tonigh. Depends how long it takes me to cleanup the microcode from my usb core :)
<emeb>
cool - let me know if you run into any snags I could help with.
<tnt>
Is there a demo app btw ? (didn't look really deep yet)
<tnt>
how is it loaded in spram ?
<emeb>
There is demo code but it's preloaded into a ROM that's implemented w/ EBR.
<corecode>
how big is the cpu design?
<emeb>
you mean how much of the FPGA does the whole thing use?
<corecode>
makes me feel like my cpu design isn't too bad
<emeb>
yours is smaller?
<corecode>
yes, around 600
<corecode>
and it is a 16 bit cpu
<emeb>
kewl
<tnt>
corecode: nice, that's about the size of my 16b cpu as well. Hard to go smaller.
<corecode>
yea, the alu mux makes it quite big
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<emeb>
hmmm... something weird going on with the ACIA. Works OK for TX but reading RX data isn't clearing the IRQ as it did in my other designs. grmbl.
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<emeb>
fixed & pushed
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