Crouzet Millenium 3

[NFAGEN 0]

Recently had to get a program out of a millenium 3 plc which I had programmed a few years ago but the cable would not connect.The only difference this time ,as my laptop no longer had a rs232 port,was the use of a USB to rs232 converter.

Having trawled the web I managed to find the circuit of the interface cable below.

It looks like the signal from the computer uses the negative going part of the pulses which aren't present on most usb to rs232 converters. Is this correct?

[pturmel 105]

The serial to USB converters that are based on the FTDI chipset have been flawless for me.  Try one of those before you go wild.