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My PC will not communicate to the programming port on my Series 90 CPU. What are the possible causes of this problem?

November 28th, 2018

There are several possibilities:

Bad port on the PC – Try using the PC’s serial port to communicate to another device in order to confirm proper operation

Bad cable – Try connecting to another Series 90 PLC in order to confirm the condition of the cable.

Incorrect communication settings in the software – The default settings for the Series 90 CPU programming port is 19200 BAUD, 8 data bits, 1 stop bit and odd parity. In cases where you suspect that the setting has changed and you have a copy of the PLC configuration, compare the CPU’s port configuration to your software’s port settings.

Bad programming port – Check the +5 volt pin (pin 5) on the programming port versus pin 7 (0 volts). If the +5 volts is not present, the fuse for that port is blown and this fuse is not field-replaceable.

If none of these suggestions solves the problem, please contact our technical support specialists at 1-800-784-9385.

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