7 Application Instructions API 50-99 2. PLC COM2 RS-485: Associated flags (Auxiliary relays) and special registers (Special D) for communication instructions RS / MODRD / MODWR / FWD / REV / STOP / RDST / RSTEF / MODRW. DVP-PLC APPLICATION MANUAL 7-106 Special register Function D1249 COM1 (RS-232) communication time-out setting (unit: ms). If users set up time-out value in D1249 and the data receiving time exceeds the time-out value, M1315 will be set ON and the error code K1 will be stored in D1250. M1315 has to be reset manually when time-out status is cleared. D1250 COM1 (RS-232) communication error code. Supported communication instructions:
MODRW Flag Function Action M1120 For retain the communication setting. After the first program scan is completed, the communication setting will be reset according to the setting in the special data register D1120. When the second program scan starts and RS instruction is being executed, the communication settings will all be reset according to the settings in D1120. If your communication protocol is fixed, you can set M1120 to On and the communication protocol will not be reset whenever RS/MODRD/MODWR/FWD/REV/STOP/RDST/RSTEF/MODRW instruction is executed. In this case, even the settings in D1120 are modified, the communication protocol will not be changed. Set up and reset by the user.
M1121 Off when the RS-485 communication data is being transmitted. By the system. M1122 Sending request. When you need to send out or receive data by RS/MODRD/MODWR/FWD/REV/STOP/RDST/RSTEF/MODRW instructions, you have to set M1122 to On by a pulse instruction. When these instructions start to execute, PLC will start to send out or receive data. When the data transmission is completed, M1122 will be reset automatically. Set up by the user; reset automatically by the system. M1123 Receiving is completed. When the execution of RS/MODRD/MODWR/FWD/REV/STOP/RDST/RSTEF/MODRW instructions is completed, M1123 will be set to On. You can process the data received when M1123 is On in the program.
You have to reset M1123 to Off when the process of received data is completed. Set up automatically by the system; reset by the user. M1124 Waiting for receiving. On when PLC is waiting for receiving data. By the system.