Chapter 8 MODBUS Communications8-8 Revision June 20108.3 MODBUS Communication ProtocolWhen using RS-232/485 serial communication interface, each ASDA-B2 series AC servo drivehas a pre-assigned communication address specified by parameter “P3-00”. The computerthen controls each AC servo drive according to its communication address. ASDA-B2 series ACservo drive can be set up to communicate on a MODBUS networks using on of the followingmodes: ASCII (American Standard Code for Information Interchange) or RTU (Remote TerminalUnit). Users can select the desired mode along with the serial port communication protocol inparameter “P3-02”. Code Description:ASCII Mode:Each 8-bit data is the combination of two ASCII characters. For example, a 1-byte data: 64 Hex,shown as ‘64’ in ASCII, consists of ‘6’ (36Hex) and ‘4’ (34Hex).The following table shows the available hexadecimal characters and their corresponding ASCIIcodes.Character ‘0’ ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’ASCII code 30H 31H 32H 33H 34H 35H 36H 37HCharacter ‘8’ ‘9’ ‘A’ ‘B’ ‘C’ ‘D’ ‘E’ ‘F’ASCII code 38H 39H 41H 42H 43H 44H 45H 46HRTU Mode:Each 8-bit data is the combination of two 4-bit hexadecimal characters. For example, a 1-bytedata: 64 Hex. Data Format:10-bit character frame (For 7-bit character)7N2 Startbit 0 1 2 3 4 5 6 Stopbit7-data bits10-bits character frameStopbit7E1 EvenparityStartbit 0 1 2 3 4 5 6 Stopbit7-data bits10-bits character frame7O1 OddparityStartbit 0 1 2 3 4 5 6 Stopbit7-data bits10-bits character frame
