I have two brand new ML1400 Series C PLCs and I am attempting to test DF1 Messaging between them. I am seeking assistance in understanding certain concepts related to channel communications. "Test1" PLC is configured as a 1/2 duplex DF1 Master on Channels 0 & 2, while "Test2" PLC is set up as a 1/2 Duplex DF1 Slave on Channels 0 & 2 (with multiple slaves to be added). Both PLCs are configured with no handshaking, CRC error detection, MSG polling, and allowing slaves to initiate with default timeouts. I have successfully written a MSG in Test1 to read from Test2 on Channel 0 using a 1761-CBL-AP00 cable. However, when I switch the MSG to use Channel 2 and connect both PLCs with an RS232 cable on Channel 2, the messaging times out. Is it possible to use an RS232 cable between both on Channel 2 as I am attempting, or are there limitations that I may be unaware of? Thank you.
Are you using a straight through or null modem (crossover) cable for your RS232 connection?
Thank you for responding. It turns out I have a straight through cable and a null modem in my possession. I wasn't aware of the distinction between the two. This information will come in handy for my networking setup.
Have you considered using Ethernet IP?
The communication will be conducted via a serial radio, as Ethernet radio is currently unavailable as an alternative.
The RS-232 null modem crossover cable successfully facilitated communication over channel 2. Gratitude to @alan_505 for enlightening me on the crucial missing component.
It sounds like you have a solid grasp of setting up DF1 Messaging, but there could be a few factors potentially causing your issue with Channel 2. RS232 communication should technically work provided there's no hardware or configuration problem. However, RS232 cables vary significantly in their pin configuration, so check if your cable matches the PLC's required pin configuration. Also verify the correct COM port is selected for Channel 2 communication in your PLC setup. Further, make sure there's no communication offset in the PLC data file that might be causing the timeout. Do double-check your baud rates, parity, and stop bits as well. Hope this helps guide your troubleshooting process.
It certainly sounds like you're on the right track! Now, while I can't see your exact setup, it's worth mentioning that Channel 2 on the MicroLogix 1400 is a 9-pin D-shell RS232 that can indeed support DF1 communications. However, keep in mind that different types of cables use different handshaking lines, which might be causing the timeout issue you mentioned. While you've confirmed that you've set up no handshaking in the PLC config, have you also made sure that you're using a 'straight-through' RS232 cable (pin 2 to pin 2, pin 3 to pin 3, and pin 5 to pin 5)? If you're using a null modem cable for instance, this could be affecting the messaging between the PLCs. Give it a try and let us know how you get on!
It sounds like you've got your setup mostly figured out! It's possible to use the RS232 cable between PLCs on Channel 2, but there're a few caveats to consider. The default baud rate for Channel 2 may be different from that of Channel 0, so ensure both PLCs are set to the same baud rate for successful communication. Also, your RS232 cable must satisfy the requirements of the particular PLC's Channel 2, meaning check your cabling diagrams to make sure it's wired correctly. Lastly, bear in mind that Channel 2 may not support all DF1 functionalities, especially if multiple slaves are connected. Personally, I would advise focusing on troubleshooting cable wiring and baud rate settings for now. You got this!
✅ Work Order Management
✅ Asset Tracking
✅ Preventive Maintenance
✅ Inspection Report
We have received your information. We will share Schedule Demo details on your Mail Id.
Answer: - Using an RS232 cable for DF1 Communication on Channel 2 between Micrologix 1400 PLCs may lead to timeouts. Consider checking the cable type and connection settings for compatibility.
Answer: - Recommended configurations for DF1 Messaging between Micrologix 1400 PLCs include setting up proper channel communications, handshaking, error detection, and timeout settings to ensure successful data exchange.
Answer: - Troubleshooting timeout issues during DF1 Messaging can involve checking cable connections, communication settings, channel configurations, and ensuring proper synchronization between Master and Slave PLCs.
Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.