[Coco] Fw: CoCo Hardware Questions

[Robert Gault]

The first thing you should do is try to find the documentation for the 
Motorola SN74LS783 / MC6883 / SAM which probably can be found through 
Google. Without having the specifics, you will have a difficult time 
determining timing.

A short answer to your questions (and I'm sure others on this list are 
better able to answer) is that the SAM synchronizes the timing among the 
CPU, RAM, and VDG chips. E and Q lines come out of the SAM going to the 
CPU. Inverse RAS, CAS, and WE lines come from the SAM to RAM. A clock 
line goes from the SAM to the VDG. Finally the SAM, a SN74LS138, and two 
PIAs permit device selection.

I won't attempt to be any more specific as I probably could not do a 
good enough job of it to be useful.

Dino Steeman wrote:
> Hi,
> 
> In an effort to understand the internal workings of the CoCo I have been
> reading
> up some books and articles, but as I only have a basic understanding of
> electronics and computer hardware, there are a lot of things that are
> unclear.
> 
 ><snip>