A1200 Clock Port Serial Card design

Probably a first, a complete but untested, design for the A1200 clock port.

Schematics, design notes and some timing diagrams included.

Why do this?

I have authored a technical note on Aminet on the clock port and received a few emails asking how to design a card for the clock port. The best way to answer the emails would have been to send a design, which I did not have. So I set about designing a serial port card to learn more. This is the result.

Why not make it a commercial product?

I have been asked to do this but considering the current state of the Amiga market, it would be hard to make a return on any outlay. I might look at producing a DIY kit.

What about software?

This is the biggest problem. A driver would need to be written. It may work with other clock port serial cards as they are of similar design but I have not tried this.

What are the specifications?

• Uses a PC16550D UART, the original from National Semiconductor that is used in most PCs, capable of 1.5MBaud, limited to 250KBaud in this design.
• The UART has a 16 byte FIFO to reduce CPU overhead.
• 250 KBPS max data rate.
• Only requires 3 ICs.

Where is the design then?

Here are the design notes, which explain how I designed this card and some decisions made.

The Schematics are here.

Some relevant timing diagrams here.

You can download everything here.

 By Ian Stedman, 19th July 2002

Updated 02 May 2011