As I understand it, the SF-7000 is fairly simple - just a flat 64KB RAM (optionally overlaid by the 8KB BIOS/IPL) and a floppy disk controller attached to another PPI chip. It's the same FDC used in the original IBM PC and a few other systems, I worked from this datasheet in my IPL disassembly:

http://www.smspower.org/dev/docs/nec-upd765a.zip

but you can implement a much reduced subset because you don't have to worry about multiple drives, disk formats, timing, DMA or error conditions. Other stuff like the parallel port can go unemulated just as easily as the SC-3000's COM port and tape input.

I ought to publish that disassembly sometime soon, it was what made me report all those Brass bugs :)

Quote: Original post by MaximZhao
As I understand it, the SF-7000 is fairly simple - just a flat 64KB RAM (optionally overlaid by the 8KB BIOS/IPL) and a floppy disk controller attached to another PPI chip.

"Quite simple" until you got to the floppy disk controller, of course...

I did try emulating it many moons ago, and used your disassembly (and documentation of the error beep codes) to try and get as far as I could, but I could never get it to work properly.