68k homebuilts

[Tony Duell]

> After doing some looking I thought I'd go with 68020 if I were to do
> 32-bit, or 68000 for 16-bit. I may take Tony's excellent advice and

IIRC, the 68020 has the feature that you can set the bus width by the 
states of a couple of pins. This was normally done to allow efficient 
access to 8-bit I/O devices (you can change the states of these pins 
depending on the current address ,of course), but there's no reason why 
you shouldn't hold the pins in the states for an 8-bit data bus and just 
have 8 it memory. Of course it's slower (4 memory cycles for each 32 it 
access), but it will work.

> try something even simpler first, if I can get my hands on the Art of
> Electronics books... they're on Amazon, I'll probably just have to
> buckle down and shell out the money.

'The Art of ELectronics' is IMHO a book every electronics engineer should 
own. There's a lot of good stuff in it. Sure there are the odd things I 
disagree with, there are things I'd do differently, but by the time 
you've read it, you'll know enough to be able to work out how you'd want 
to do things.

My criticism of the Student Manual is that as it was written for a 
university course, it assumes you have access to some nice test gear 
(like a 'scope, bench PSU, etc). This means the esperiments possibly 
can't be done by the average hobyist just starting out. But again there's 
a loot of good stuff in it, and I don't think you need too much exotic 
stuff for the 68008 circuits.

-tony