I have an Allen-Bradley MicroLogix 1400, and have been working with it for a few months now and understand its basics pretty well. Up to now I've been using Modbus TCP (EtherNet) to communicate to a SCADA system through a Field Processor.
However, now I have to use Modbus RTU (RS-232) and am encountering difficulties. It's not sending data. In one of the attached images, the embedded display is shown and the box corresponding to channel 2 (RS-232, for Modbus RTU) is not checked (sorry for the poor quality picture).
As far as I know, the only settings I have to configure are those I've shown in the attached images. The node, baud rate, parity, stop bits, and data bits all match those set in the FP and SCADA system, and all of it looks good to me. The serial cable being used is also a reliable one, I've used it with remote I/O devices with no hassle just yesterday.
Transmitting the data I need with Modbus TCP is fine, but RTU is just not transmitting data for me. If anyone has any advice it would be greatly appreciated.
EDIT One: More Information
The SCADA system is the Master, and as far as I can tell it is requesting data from the Slave (the ML1400) appropriately. Although I've just noticed that in the "Channel Errors.png" image attached, it isn't showing any messages received. That seems like a problem.
EDIT Two: Messages Received
I left the PLC online to do some minor edits to the program, and apparently it received some messages when I wasn't looking (please see attached image "Channel Errors with Msg Rec.png"). I made no changes to the communications, so I'm not sure what happened there, but it happened, which is good proof that at least there's connectivity.
However, now I have to use Modbus RTU (RS-232) and am encountering difficulties. It's not sending data. In one of the attached images, the embedded display is shown and the box corresponding to channel 2 (RS-232, for Modbus RTU) is not checked (sorry for the poor quality picture).
As far as I know, the only settings I have to configure are those I've shown in the attached images. The node, baud rate, parity, stop bits, and data bits all match those set in the FP and SCADA system, and all of it looks good to me. The serial cable being used is also a reliable one, I've used it with remote I/O devices with no hassle just yesterday.
Transmitting the data I need with Modbus TCP is fine, but RTU is just not transmitting data for me. If anyone has any advice it would be greatly appreciated.
EDIT One: More Information
The SCADA system is the Master, and as far as I can tell it is requesting data from the Slave (the ML1400) appropriately. Although I've just noticed that in the "Channel Errors.png" image attached, it isn't showing any messages received. That seems like a problem.
EDIT Two: Messages Received
I left the PLC online to do some minor edits to the program, and apparently it received some messages when I wasn't looking (please see attached image "Channel Errors with Msg Rec.png"). I made no changes to the communications, so I'm not sure what happened there, but it happened, which is good proof that at least there's connectivity.
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