ASDA-M Chapter 9 Communication9-8 Revision December, 20149.3 MODBUS Communication ProtocolThere are two modes of MODBUS networks communication, ASCII (American StandardCode for Information Interchange) mode and RTU (Remote Terminal Unit) mode. Userscould set the needed communication protocol via parameter P3-02. Apart from these twocommunication modes, this servo drive also supports function of 03H to access more thanone data, 06H to write one character and 10H to write multiple characters. Please refer tothe following descriptions. Code DescriptionASCII Mode:The so-called ASCII mode is using American Standard Code for Information Interchange(ASCII) to transmit the data. Between two stations (Master and Slave) to transmit data 64H,the master will send‘6’which represented by 36H of ASCII code and ‘4’ representedby 34H of ASCII code.ASCII code of digit 0 to 9 and characters A to F is as follows: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:Every 8-bits of data is constituted by two 4-bits hexadecimal characters. If data 64H istransmitted between two stations, it will be transmitted directly, which is more efficient thanASCII mode. Character StructureCharacters will be encoded into the following framing and transmitted in serial. Thechecking method of different bit is as the following.10 bits character frame (for 7-bits 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 frame
