Modbus Communication - Parker FL-20-C Series Product Manual

6.2 MODBUS Communication

6.2.1 Introduction of MODBUS communication
Servo drive provides RS485 communication. The following description shows the contents
related to the communication protocol, hardware interface etc.
6.2.2 MODBUS Overview
Modbus is a serial and asynchronous communication protocol. Modbus protocol is a general
language applied to PLC and other controllers. The protocol defines an information structure
that can be identified and used by controller regardless of whatever network they are transmitted.
Modbus protocol does not need the special interface; the typical physical interface is RS485.
User can read reference books or ask for the details of MODBUS from manufactures.
6.2.3 MODBUS Communication Protocol
I. Overall Introduction
1. Transmission Mode
(1) ASCII transmission mode
In ASCII mode, one Byte (hexadecimal format) is expressed by two ASCII characters.
For example, 31H (hexadecimal data) includes two ASCII characters'3(33H)','1(31H)'.
Common characters, ASCII characters are shown in the following table:
Characters
ASCII Code 30H
Characters
ASCII Code 38H
(2) RTU mode
In RTU mode, one Byte is expressed by hexadecimal format. For example, 31H is delivered to
data packet directly.
2. Baud Rate
Setting range: 2400, 4800, 9600, 19200, 38400, 57600.
3. Frame Structure
(1) ASCII mode
Byte
1 Start Bit (Low Level)
7 Data Bit
0/1 Parity Check Bit (None for this bit in case of no checking. Otherwise 1 bit)
1/2 Stop Bit (1 bit in case of checking, otherwise 2 bits)
(2) RTU mode
Byte
1 Start Bit (Low Level)
8 Data Bit
0/1 Parity Check Bit (None for this bit in case of no checking. Otherwise 1 bit)
1/2 Stop Bit (1 bit in case of checking, otherwise 2 bits)
'0' '1'
31H 32H
'8' '9'
39H 41H
Function
Function
FL20-C Series
'2' '3'
33H
'A' 'B'
42H
96
'4' '5'
34H 35H
'C' 'D'
43H 44H
'6' '7'
36H 37H
'E' 'F'
45H 46H