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 to include this sheet to the main schematics when I build and test the circuit, so for now this is the only reference. Click on the image to zoom in.

The board provides two serial ports and connects to the CPU by means of a 64-wire ribbon and a DIN41612 connector (like my memory card) and to external devices by two DB9 connectors. I used two 16C550 chips (one per each port) and four MAX232CPE devices (two per each port, as one MAX232 can convert up to four signals, while the full RS/232 specification has eight). I also used a 1.8432MHz oscillator, typically employed in such applications to generate common serial communication baud rates. Now I am going to build it and give it a try. Altogether, it is a simple circuit in terms of number of devices but I may still have some fun making it work. This time I was not simulating anything, so the actual hardware will be my first prototype.

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