Hi Geoff,

Thanks for the info and the tests you've done.

From your tests it seems to me now clear that the Einey side
of mode 1 does work with the specified hand shaking. I made
this assumption a couple days ago and thought I had better
check out the PC side of things.

In brief: On the Einey I set up the port b in mode 3 set bit
0 pin 2 for output the rest left as inputs. I made a circuit
using 303 resister and a LED connected to data pin 0. The
LED lit up but not very brightly.

If I connected the LED circuit to 5v pin 1 of the user port
the LED came on much brighter.

I tried an analog switch TC4016BP ic scrimped off an old
Einey mother board connecting 5v pin 1 through the IC to the
LED and data pin 2 bit 0 of the user port to the gate of the
IC the LED lit but only dimly.

Next I connected a wire from 5v pin 0 to the gate of the IC
the LED lit up bit more brightly but not as bright as
directly connecting the LED circuit to 5v pin 1.

It seems the outputs of the user ports are week on power.

With the above knowledge I tried the connections to the PC
printer port. Just a connection for ground and pin 10
Acknowledge of the centronics plug on the printer cable
connected to the PC.

On the PC I have a program running which sets the ECP
parallel port to byte mode and pols the status port for the
state of acknowledge.

Here is an irritation! Information off the web says that
reading the inputs of the status port will always show high
if there is nothing connected to the port. No one seems to
be saying how the PC is to know that there is something
connected. Never the less after fiddling with wires my
program does read acknowledge as low when there is no power
supplied to the acknowledge pin.

Ok connecting 5v pin 1 of the user port to pin 10
acknowledge for the PC printer port does get my program
polling acknowledge as high and disconnecting puts it back
to polling low.

Connecting the output pin 2 data bit 0 to acknowledge makes
no difference. As with LED circuit I tried to use the data
output as a gate switch for the IC with power from pin 1 5v
going through IC to acknowledge. This did not work. Putting
5v from pin 1 onto the gate of the IC also didn't work.

I tried a transistor of unknown specs this did not switch
power with data pin going to the gate but did when I wired
5v from pin 1 to the transistor base.

It seems outputs from the user ports are too week in
themselves to register on the PC printer port.

Volt meter reading for data pin 0 was around 3.4v for pin 1
4.94v.

Surfing for answers on the web there is a suggestion that an
op-amp would be the option to boost power on week out put
lines. If I can find one I'll try this.

Many Thanks for your time and effort.

Regards Chris Coxall