Serial communication


A good way to communicate with e.g. a PC is serial communication.

For this type of communication (a null modem) you need a serial port like a CPS or an SCA add-on on the PCW: the PC should have one fitted standard. I use a cable with the 25-pin RS 232 C connector on both sides, but the smaller 9-pin version is also suitable: use an adaptor or change the wires according to the 9-pins layout.

This page only covers the connection with a PC (RS232) but there is a lot more data available for other type of computers (e.g. the Apple Macintosh using RS422): contact me for other types of computers. A null modem cable (check the lay-out) should be purchased or soldered with the following layout:

pin 2 to opposite pin 3
pin 3 to opposite pin 2
pin 5 to opposite pin 20
pin 7 to opposite pin 7
pin 20 to opposite pin 5

the pins 4, 6 & 8 should be 'short circuited' on the same side of each of the connectors.

Buying one in a computer shop does not guarantee that you have the right type, because there are so many different types of computer (and corresponding matching cables) Converting a standard RS232 cable to this layout is the best option: make sure you get a cable with detachable connectors! A soldering iron will do the rest. The finished product is shown on the right.

After the matter of hardware has been settled the software should be considered. I highly recommend good old Kermit, a comms program that is available for both the PCW as the PC.

MSKERMIT.ZIP (73,910 bytes, including manual). Version 3.0, 1990, old but works.

KERMPCW.ZIP (15,081 bytes, including manual). Kermit-80 version 4.08. Version patched for use with an Amstrad PCW with a SIO add-on serial interface.

Contact me for a 3" disk for the Amstrad PCW version (you will, most likely, not have access to a conversion program to get it into the PCW - otherwise you would not need a null-modem). After having installed suitable versions of Kermit on both computers transferring files is just a matter of giving commands like RECEIVE and SEND. Works like a dream, though restricted to 9.600 baud rate and a distance of a couple of meters! The settings for the PC version are typically (set port to) COM2 and (set speed to) 9600.

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