TECO JSDEP Series - Chapter 7: Communications function; 7-1-3 Modbus Communication Protocol for RS-485

7-7
7-1-3 Modbus communication protocol for RS-485
z The MODBUS protocol allows an easy communication within types of network
architectures,before start to communication with slave device, set the ID number
( Cn036 ) for Servo drive respectively, server distinguish ID number for controlling
specific client station.
z Standard Modbus networks combine two transmission modes: ASCII or RTU:
ASCII(American Standard Code for information interchange) Mode and RTU (Remote
Terminal Unit) Mode, Use Cn038 to select ASCII or RTU mode.
Coding method
ASCII Mode
8-bits Data consist of two ASCII code.
Ex: Data 26H 1-byte , the ’26’ convert to ASCII code is include character ’2‘ Æ <32H> and ’6’
Æ<36H>
ASCII Chart ( 0 ~ 9 and A ~ F ):
Character ‘0’ ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’
ASCII
code(Hex)
30H 31H 32H 33H 34H 35H 36H 37H
Character ‘8’ ‘9’ ‘A’ ‘B’ ‘C’ ‘D’ ‘E’ ‘F’
ASCII
code(Hex)
38H 39H 41H 42H 43H 44H 45H 46H
RTU Mode
Each 8bits is consist of 2 Hex number (4-bits per Hex number).
Ex.: Data 26H, the data length is 1-byte.