Made a small bit of progress this morning, and also a small setback.
1st the setback, when trying to sniff the serial data via using a laptop and one of my prolific usb serial adapters, as I load the lathe control software I see a burst of data on the terminal screen, but the lathe control software then fails to see the controller. This happens no matter if I tap into the TX or RX lines of the lathe serial cable, so I am guessing the data lines are getting pulled to low for the lathe controller to cope.
I have not yet confirm that be using my scope, but I will be having a closer look later on today.
EDIT:
Just tested the serial voltages again but with the usb serial adaptor.
TX Line from the computer, 8.90v peek to peek, -8.12v to +781mv.
RX Line from the computer, 8.90v peek to peek, -7.96v to +937mv.
Without the usb serial adaptor connected to the TX & RX lines, I get the following voltages.
TX Line from computer, 20.79v peek to peek, -10.16v to +10.63v.
RX Line from computer, 16.40v peek to peek, -8.75v to +7.65v.
I have been able to pull some data from the TX and RX lines by using the picoscope and it's built in serial decoding.
9600bps does indeed seem to be the correct baud rate.
Something I did find strange is once the lathe control software is loaded and you are at the 1st loaded screen there is no watchdog, no data at all to or from the control board, It's not unto you go into one of the other screens, that the watchdog kicks into live.
I have turned the serial decoding to ASCII, and can see while the system is at idle it sends out a single ascii character, the control board reply's with the same character then 133ms later the controller sends a bunch of data.