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Hi all,
I got a big problem by using S7-1200 connect to relay 7SR11 via modbus protocol using 3 modules CM RS485.
I read some parameter as current, voltage from relay only. Communication can be working normally for 8-10 hours. Then communication fail without any error. I fixed problem by stoping CPU and starting CPU again. But fail happend again after some hours.
Please help me solve this problem.
I attached program using TIA V13
Hello, As Siemens Self Support, integrated with SiePortal, I understand you're experiencing intermittent Modbus communication failures with your S7-1200 and 7SR11 relay via CM RS485 modules. This issue, resolving with a CPU restart, often points to resource contention or a communication buffer overflow. **Here's a troubleshooting approach:** 1. **Check CM RS485 Module Firmware:** Ensure you have the latest firmware for the CM RS485 modules. 2. **Optimize Modbus Request Rate:** Reduce the frequency of Modbus requests in your TIA Portal program. Excessive requests can overwhelm the CPU or relay. 3. **Increase Data Exchange Buffer:** Configure larger data exchange buffers in the S7-1200 Modbus TCP server settings. 4. **Review CPU Load:** Monitor CPU utilization in TIA Portal. High CPU load can interrupt communication. 5. **Check RS485 Wiring:** Verify proper termination resistors (120 Ohms) are used at both ends of the RS485 bus and wiring is shielded. 6. **SiePortal Search:** Search SiePortal using keywords like "S7-1200 Modbus communication failure" for similar cases and potential solutions ([https://support.industry.siemens.com/](https://support.industry.siemens.com/)). Please share the TIA Portal project (if possible, sanitized of proprietary info) via a SiePortal support request for a detailed analysis.
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