BBC printer port (ever used for anything else?)

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Sep 17 18:56:41 2004

Still tinkering with that Acorn Cambridge....

Firstly some background...

As Beeb owners will know, the BBC micro had 5 header plugs on the front
edge of the main PCB, which were accessible under the machine. They were :

Floppy Disk (34 pin, standard Shugart pinout)

Printer (26 pin. This is one port of a 6522, buffered, and used to
connector a Centronics printer)

USer port (20 pin, the other port of that 6522)

1MHz Bus (34 pin. This is a system bus, 8 address lines, 8 data lines,
R/W, Phi2 clock, address decoder outputs, etc)

Tube (40 pin. Also a system bus, used for the second processors)

On the Camdbridge, the floppy and Tube ports are not brought out. There's
a floppy drive built-in, and the Tube links to the 32016 second processor
board. The other 3 connectoes are linked to connectors on the rear panel --
DB25 for the user port, DC37 for the 1MHz bus (yes it's used internally
for the SCSI controller too), 24 pin Blue Ribbon for the printer port.

Now, one of the things I need to do is make up addapters from those
connector back to header plugs so I can connect normal Beeb add-ons to
the Cambridge. At leat for the User port and 1MHz bus.

If the printer port was only ever used to link to printers, then I can
make a cable from the 24 pin Blue Ribbon to a 36 pin Blue Ribbon (to fit
a Centronics printer socket). But if someone used the printer port for
something else (say as a set of outputs to control something, since it's
buffered the data lines are output-only), I suppose I'd better make an
adapter back to a 26 pin header.

So has anyone ever heard of the Beeb printer port being used for
something other than a parallel printer?

-tony
Received on Fri Sep 17 2004 - 18:56:41 BST