7 Application Instructions API 50-99 DVP-PLC APPLICATION MANUAL 7-108 Special register Function D1122 Residual number of words of transmitting data. D1123 Residual number of words of the receiving data. D1124 Definition of start character (STX) Refer to the following table in point 3 for the setting. D1125 Definition of first ending character (ETX1) in the RS instruction Refer to the following table in point 3 for the setting. D1126 Definition of second ending character (ETX2) in the RS instruction Refer to the following table in point 3 for the setting. D1129 Communication time-out setting (unit: ms) If the value in D1129 is 0, there is no communication timeout.
If the setting value in D1129 is greater than 0, and the first character is not received when RS / MODRD / MODWR / FWD / REV / STOP / RDST / RSTEF / MODRW is executed, or the time interval between two characters is greater than the setting value, the PLC will set M1129 to ON. Users can deal with the communication timeout by means of the flag. After the users deal with the communication timeout, they have to clear M1129. D1130 Error code returning from Modbus. D1168 The specific end word to be detected for RS instruction to execute an interruption request (I150) If the character received is equal to the low byte in D1168, the interrupt I150 will be triggered.
D1169 The specific communication length to be detected for RS instruction to execute an interruption request (I160) If the length of the data received is equal to the low byte in D1169, the interrupt I160 will be triggered. If the value in D1169 is 0, the interrupt is not triggered. D1256~D1295 When the RS-485 communication instruction MODRW is executed, the command sent is stored in D1256 ~ D1295. Users can see the contents of the registers to check whether the command is correct. D1296~D1311 The PLC automatically converts the received ASCII data into hex data. Supported communication instruction: MODRW