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Showing results for tags 'V1040 RS485 RS-485'.
Hello Everyone, I have problem with communication between V1040-T20B and any Modbus slave. Unitronics configuration: Visilogic 9.7.0 V1040-T20B Firmware 003.003.11 Boot 002.002.11 Bin library 003.010.03 Factory boot 001.003.07 When RS-485 is used the PLC receive the same data as it transmit. After short time it receive the correct data from the slave. But the V1040 evaluate transmitted data as answer and produce an error. Then correct answer come but V1040 ignore it. When I tried Vision 120, everything works fine. The PLC disable recieving data while the PLC is transmitting own data. But with V1040 it does not work on both port. RS485 Termination jumpers does not help. On PLC information mode Serial monitor is visible that PLC receive the correct data from RS485 slave, but it is visible, that it always recieve 2 packets for one transmitted packet. Because first packet is wrong (own transmitted data) and second is ignored nothing can be read from RS485 slave to PLC MI's. I see two solution for this problem: 1. There is SP3072EE chip for transmit/recieve with Read Enable pin. This pin can be used to disable receiving data during transmit. 2. Clear Receive buffer immediately after finishing transmit Is it possible to solve this problem by upgrading firmware or other software way? With best regards David