4- 1CommunicationsThis chapter introduces information regarding the communications ports of the PLC.Through this chapter, the user can obtain a full understanding about PLCcommunication ports.Chapter Contents4.1 Communication Ports.................................................................................................... 4-24.2 Communication Protocol ASCII mode .......................................................................... 4-34.2.1 ADR (Communication Address) ......................................................................... 4-34.2.2 CMD (Command code) and DATA ..................................................................... 4-44.2.3 LRC CHK (checksum) ....................................................................................... 4-54.3 Communication Protocol RTU mode ............................................................................ 4-74.3.1 Address (Communication Address) ................................................................... 4-74.3.2 CMD (Command code) and DATA ..................................................................... 4-74.3.3 CRC CHK (check sum) ..................................................................................... 4-84.4 PLC Device Address .................................................................................................... 4-104.5 Command Code ........................................................................................................... 4-124.5.1 Command Code: 01, Read Status of Contact (Input point X is not included)..... 4-124.5.2 Command Code: 02, Read Status of Contact (Input point X is included) .......... 4-134.5.3 Command Code: 03, Read Content of Register (T, C, D) ................................. 4-144.5.4 Command Code: 05, Force ON/OFF single contact ......................................... 4-154.5.5 Command Code: 06, Set content of single register .......................................... 4-164.5.6 Command Code: 15, Force ON/OFF multiple contacts .................................... 4-164.5.7 Command Code: 16, Set content of multiple registers...................................... 4-17
