Ascii comms with ML1100 and AHL instruction

Hello

I am using an AB Micrologix 1100 to read ASCII comms from a device that has an opto-isolated port. I need to set RTS low and DTR high to power up the opto isolator. I am using CH0 in ASCII mode with no handshaking. I tried using the AHL instruction to set the DTR bit permanently on, but I could not get it to work. I find that the instruction manual seems to disagree with the online help and I just wondered if anybody has ever tried to use this instruction before? I have tried all combinations of the AND and OR masks. In the end I set my comms for CH0 to Full Duplex Modem (RTS on) and made an adaptor to hard wire the RTS pin to the DTR pin as a way of setting the DTR on, but its not very neat.

Thanks
Al

Your jumper method is probably going to be the best one.

The MicroLogix 1100 doesn't have DCD, DTR, or DSR pins on the Channel 0 port. RA replaced them with the Data A and Data B pins for the embedded EIA-485 port instead.

Thanks Eddie I should have checked that. Looking at CH0 it has

1 RS485 B+
2 Ground
3 RTS
4 Rxd
5 DCD
6 CTS
7 Txd
8 RS485 A-

I am still puzzled by the AHL instruction though, maybe it only works for handshaking and not for setting say RTS permanently on?

Al