Re: Theorizing: cloning CBM electronics with modern technology.

From: Michal Pleban <*lists_at_michau.name*> Date: Sun, 27 Mar 2022 17:03:20 +0200 Message-ID: <acbfcada-1b52-1d49-6661-92305fe14a5a_at_michau.name> · lists_at_michau.name

ruud_at_Baltissen.org wrote on 23.03.2022 21:08:

> But to be honest, I lean more to an even simpler solution:
> connecting the SD card directly to the 6522. But I'm sure this will
> come with a penalty: speed. IIRC the 1541 collects a byte from the
> floppy every 23 uSec. Collecting 8 bits by bit banging and rolling
> them into a byte will cost much more time:
> - toggle clock bit of SD
> - read bit into bit 7
> - roll bit into Carry
> - roll Carry into end byte
> - toggle clock bit of SD
> Rough guess: 17 uSec for one bit?
> Let's face it (again) Ruud, the uController solution is better.

It shouldn't be so hard to speed this up with two TTL shift registers + 
some glue logic?

Or, just implement a SPI controller in a CPLD that can be attached to 
the 6502 bus. In fact that's what I did some 8 years ago.

Regards,
Michau.