gabe Posted December 15, 2016 Report Share Posted December 15, 2016 Hi y'all: I've been using M-91 PLCs successfully in various applications and only recently came across a customer supplied M91-2-T1 that does not seem to be able to establish communication to program via the RS232 port. The PLC powers up fine as I see the old legacy program running on the hardware; however, whenever I try to download some test ladder logic, or even pull some PLC data, I get the "Communication could not be established" error message. Things that I've tested: 1) The COM port has been verified 2) I've verified the function of the programming cable chain: Serial adapter and Unitronics MJ10-22-CS25 cable verified by using the same setup to program two different M-91 PLCs that I had lying around (for completeness, these were the M91-2-R6C models - so not an exact match). 3) I've tried adjusting internal jumpers for all combinations of RS232 and RS485 4) I've tried using the "i" button on the PLC to match the RS232 parameters to that of the PC. In case it matters, the M-91 PLC in question has the following specs as indicated using the "i" button: Model: M91-2-T1 HW Rev: A O/S Version: 3.80 O/S Build: 05 Anybody have any troubleshooting thoughts or run into something similar? Quote Link to comment Share on other sites More sharing options...
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