10 Application Instructions API 202-313 Points to note: Relative flags and special D registers of COM2/COM3 :
DVP-PLC Application Manual 10-12 COM2 COM3 Function Description M1120 M1136 Retain communication setting Protocol M1143 M1320 ASCII/RTU mode selection setting D1120 D1109 Communication protocol D1121 D1255 PLC communication address Sending M1122 M1316 Sending request request D1129 D1252 Communication timeout setting (ms) Receiving M1127 M1318 Data receiving completed completed - M1319 Data receiving error - D1253 Communication error code M1129 - Communication timeout setting (ms) M1140 - COM2 (RS-485) MODRD/MODWR/MODRW data receiving error Errors M1141 - MODRD/MODWR/MODRW parameter error (Exception Code exists in received data) Exception Code is stored in D1130 D1130 - COM2 (RS-485) Error code (exception code) returning from Modbus communication