18 Nov
2008
18 Nov
'08
2:34 p.m.
On 17 Nov 2008 at 18:55, Tony Duell wrote:
Well, that it curious. I would have thought very few devices had +/-12V
supplies and a TTL level serial port (given the former, adding the
buffers to RS232 is trivial and cheap, and makes the device a lot more
useful).
Is there anything else in the nnit apart from
1488s and 1489s and PSU
parts? Any logic?
Is there any maker's name on the unit or on the PCB?
Tony, from the photos, it's a homebrew, built on a piece of
protoboard with hand wiring between the pads. No other logic, just
1488/89 ICs, which means that a supply of +/-12 or so had to come
over the cable.
Being homespun, it's hard to say what this might fit, although a
serial adapter for an early printer (the Epson MX-80, for example,
was sold with only the parallel adapter, even though serial comm
logic was present. The "serial" board was pretty much just level-
shifting to RS-232 levels.
I beleive there were actually 2 serial adapters for Epson dot matrix
printers. One was just buffers, fonfig switches, and minimal logic. I
_think_ the serial port was bit-banged on one of the printe
microcontrollers, I don;t think said microcontroller has a hardware UART.
The other serial interface contained a microcontorller and buffer RAM,
and was essentially an RS232->Centronics interface.
I guess there were +/-112V supplies on the intenral interface connector
of the Epson printer. But I think you had to add some configuration
switches (which IIRC were read over the port normally used for Centronics
data ioput) to make it useful. So I dout that's what this device is for.
As an aside, somewhere I have what appears to be a GPIB interface board
for an Epson dot matrix printer. I must dig it out and try it...
-tony