Hello everyone, I am currently attempting to establish Modbus communication using the CB1241 RS485 Communication Board with a Siemens S71200 PLC. The CPU I am utilizing is the 1215C. Despite successfully configuring the hardware and writing a program for Modbus communication, I am facing an issue where the RxD and TxD LED indicators on the communication board are not illuminating. Upon checking my configuration, I have confirmed that the PLC has recognized the module when I connect online through TIA Portal. However, data transmission and reception are not occurring as the LEDs on the board remain inactive. The functions "MB_COMM_LOAD" and "MB_MASTER" in my program show no errors and have a 16#0000 Status. I am seeking suggestions on potential issues or errors that may be causing this problem. Any insights on this matter would be greatly appreciated.
Hello everyone, I am currently working on setting up Modbus communications using the CB1241 RS485 Communication Board with a Siemens S71200 PLC equipped with a 1215C CPU. Despite successfully configuring the hardware and programming the MODBUS communication, I am facing an issue where the LED indicators for RxD and TxD on the communication board are not illuminating. While checking my configuration and verifying module recognition through TIA Portal when online, it seems that the PLC is not transmitting or receiving data as intended. The functions "MB_COMM_LOAD" and "MB_MASTER" in my program show no errors and a 16#0000 status. Are there any suggestions on what could be causing this issue or where the problem lies? I've come across information online suggesting that the board on the 1215C CPU might become non-functional if the CB1241 module was inserted while the PLC was powered, and I am considering if this could be a factor. My current software version is TIA Portal V17.
When data is being transmitted or received through the communication port, these LED lights will illuminate. Which specific device is the board communicating with during this process?
tarik1978 inquired about the LED indicators on the board, which only light up when data is being sent or received through the communication port. The board is currently connected to a Vaisala WXT536 Weather Station. How can I ensure that data is properly transmitted and received through the port with the correct settings in place?
To troubleshoot communication issues with WXT536 weather stations, begin by verifying the default address which is 1. Swap the RS485 wires to ensure proper connections. Check the termination resistors for any issues. Additionally, make sure that the firmware version of WXT536 is 3.85 or higher for optimal performance.
To ensure proper functionality, verify that the MODE parameter in the instance data of "Modbus_Comm_Load" is configured for half duplex RS485 communication (set to 4). Additionally, confirm that the "optimized block access" feature is turned off in data block DB14.
Hi there, It sounds like you've covered a lot of the bases in your troubleshooting, so kudos to you for that. One possible issue could be to do with the termination resistors on your RS485 network. The RS485 standard requires termination resistors at both ends of the bus to prevent signal reflections. If these are absent or incorrectly valued, it may cause communication problems. Check if they are connected and their values are right around 120 ohms. Also, ensure your wiring is correct. RS485 uses differential signaling, so the wiring can get complex. The 'A' terminal of your Master device should connect to the 'A' terminal of your slave device(s) and vice versa for the 'B' terminal. Finally, ensure your Modbus register addresses and data formats are perfectly matched between your Slave and Master device, lest there be addressing errors. Hope this helps!
It sounds like you've already done some thorough troubleshooting! Since the RxD and TxD LEDs aren't lighting up, it's worth double-checking your wiring connections to ensure they are secure and correctly aligned with the Modbus protocol. Also, consider reviewing your baud rate and parity settings in both the PLC and the connected Modbus device to ensure they match. Sometimes, signal integrity issues can arise with long wiring or improper termination, so if you haven’t already, try keeping your setup as close to the recommended distances as possible. If these don’t solve it, it might be helpful to check for any firmware updates for your communication board—there could be known issues that have been addressed. Good luck!
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Answer: - The issue could be related to a potential error in the configuration or program setup that is preventing data transmission and reception. Further troubleshooting may be required to identify the specific cause of the problem.
Answer: - You can start by checking for any errors or issues in the configuration settings for the Modbus communication and ensuring that the "MB_COMM_LOAD" and "MB_MASTER" functions in your program are functioning correctly. Verifying the wiring connections and communication parameters can also help in troubleshooting the problem.
Answer: - The "160000 Status" displayed by these functions may indicate that the communication setup is correct but data transmission or reception is not occurring as expected. Additional troubleshooting steps may be needed to pinpoint the exact cause of the problem and resolve it effectively.
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