Building a 68000 Single Board Computer - Revision 2.1

I've now updated the design with some changes that I call revision 2.1. It is in a different github directory from revision 2.0: https://github.com/jefftranter/68000/tree/master/TS2/v2.1

In revision 2.1, the large and hard to obtain MC14411 baud rate generator is replaced by a smaller, simpler circuit using the more easily obtained 74HC4060. The difficult to obtain 25LS2548 chip is replaced by more commonly available parts.

Both circuit changes were tested with the wirewrap prototype and a breadboard.

I've done a new PCB layout and checked it reasonably carefully. I'm confident enough in it that I have ordered some boards from easyeda.com. These will take some time to arrive. I plan to build up one board using the parts from the wirewrap prototype.