Connecting an external modem to a PLC can save a machine builder a ton of time and labor if that one day is required to troubleshoot your machine 1000 miles away. Allen Bradley offers modem kits that can be installed, however if your trying to save some money why not just use a plain old fashion US Robotic External modem?

Configuration requires two steps:

1. Configure your DF1 port on your Micro Logix 1500 LRP or SLC 5/03 port.
2. Configure your US Robotic modem.

If you are using a Micro Logix 1500, make sure you purchase the LRP model. The LRP model gives you an additional DB-9 port on the side of the processor that you can dedicate to your modem.

First lets configure our DF1 port to the following settings. If you are using a Micro Logix 1500 your port channel will most likely be Channel 1 (the side port). If you are using a SLC 5/03 chances are your port will be Channel 0 (the only DB-9 port on the front of the CPU).

Open up RS Logix 500 and click on Channel Configuration. Setup the channel setting like so:

Current communication mode = SYSTEM
System mode driver = DF1 FULL-DUPLEX
User mode driver = ASCII

CH 0 or CH 1 SYSTEM CONFIG
BAUD = 9600
STOP = 1
Duplicate detect = unchecked
Ack time out = 150
SRC DEC ID = 9
Control line = Full-Duplex modem
Parity = none
Error detect = BCC
Nak retries = 3
Enq retries = 3
Embedded responses = Auto-detect

Download your new Channel Configuration using RS Linx.

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