It talks! 5

It talks!
I now have a computer with support for RS-232 serial communications. Since my last post I managed to build and preliminarily test the new device card with two 16550 UART chips. Somehow it makes me very excited, because for the first time I will be able to communicate with my system by means of keyboard ...

UARTs board draft schematics

UARTs board draft schematics
I completed the initial revision of UARTs board schematics last night. Both 16550 UART chips and MAX232 level converters were new to me, so the task took several hours. Unlike with simple TTL chips, this time I really had to study the datasheets carefully to understand what all those pins do. I am only going ...

Serial ports (based on 16550D UARTs) 5

Serial ports (based on 16550D UARTs)
With the CPU completed, it is time to think of an I/O to be able to play with the system somewhat more interactively than by plugging EPROM chips in and out and attaching logic probes to data and memory buses. At first, my plan was to build a PS/2 keyboard controller (input) and a rudimentary ...