Catch-up to realtime

A project log for Cat-644

An 8-bit computer based around an AVR ATMega-644 and junk-box SRAM.

marsMars 08/11/2014 at 16:440 Comments

I've been writing a 'backlog' of project logs, documenting parts of construction that I did before joining  There are still a few updates in the backlog, but there is a quick real-time status update.

First:  A mess of wires:

The whole thing is off the breadboard!  It's been off the breadboard for a while.  The design was originally split into two boards.  The bottom board has the CPU, oscillator, rs-232, and the top board has RAM, video and SD card.  When I was experimenting, I thought the RAM and video design would change a lot, so I wanted flexibility.  I built the CPU board first, and connected it through a ribbon cable (40-wire common 'IDE' cable) to the breadboard.  I thought that a ribbon cable would make a good backplane, and the commonly availabile IDE, with 3 connectors, would let me have 3 boards, if I wanted to add lot of expansion.  I ended up quickly stabilizing on a simple design, and in retrospect it all would have fit on one board.  Any future CAT-644 builds will be single-board, although I will probably keep the ribbon cable to allow for expansion.

I've also been working on a case.  I had two ideas for a case.  The first, is a simple box.  The CAT-644 board(s) can be put in a compact rectangular case.  The case would have stanfard PS/2 and VGA connectors on it, and it can just 'live' on a desk, with all the other computers, and even share screen and keyboard through a standard KVM.  This is the more practical form factor, and eventually my CAT-644 will end up in a case like that.

But, for now, I really wanted to create a classic 80's 8-bit micro.  This means the computer and keyboard all in one box.