68k homebuilts

[Henk Gooijen]

> Date: Fri, 12 Dec 2008 16:23:00 -0600
> From: ethan.dicks at gmail.com
> To: cctalk at classiccmp.org
> Subject: Re: 68k homebuilts
> 
> I have a bit of experience with the 68008 and 68000/68010 from the
> design end (they were used in various released and unreleased COMBOARD
> products)
> 
> ... At 4MHz to 8Mhz, it shouldn't be a problem these days unless you
> have a particular VLSI chip you want to use for I/O (6821, 6522, etc.)
> and it isn't fast enough.
 
The 68k CPU even provides signals to interface the 6800/6809 era I/O
peripheral chips like the ACIA, PIA and PTM. The 68k synchronizes to the
E clock when VPA is asserted.  The 68k is really easy to use together
with SRAM and simple I/O. I have designed one for my StarShip when I
discovered that the 6802 was no longer sufficient. In the end, the 68000
was replaced by the pin-compatible 68010 (but the '010 has a different
stack frame, so interrupt (exception) processing (in the OS) has to be
adapted. And now I am using a VME bus card with an 68020 at 30 MHz.
Should pick up that hobby again!
So little time, so many (geeky) things to do ...
 
- Henk.