CPCI RS232 Interface

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Octoate's self-built version of the CPCI RS232 interface

This RS232 interface was published as a DIY project in a special edition of the the German magazine: CPC Schneider International Sonderheft (#3-1986) and also in a later issue.

As the standard CPC series does not include a RS232, this interface was very handy in order to communicate with other computers(eg. IBM PCs). A major drawback was the missing interrupt line which means that your programs have to poll the interface.


A terminal program, written by The Cranium, for this serial interface was published in the last issue of the CPC Schneider International (12/1 1992/1993).

Technical specs

Contains a single 25pin DSUB connector, a MC6850 chip (ACIA), MAX 232 voltage converter, 74LS138 and 74LS85 address decoders, and a 4MHz oscillator with HEF 4060 clock divider, the clock divider connects to a mechanic switch, allowing to select between 19.2kHz and 38.4kHz. Four dip-switches allow to select the port addresses (FxDCh and FxDDh, with x=0..F, usually x=8).

 F8DCh CPCI Serial Interface MC6850 Control/Status Register (R/W)
 F8DDh CPCI Serial Interface MC6850 Data Register (R/W)

How to build a RS232 interface (German)