EURA SD20-G Series, Manual

Page: 340 / 353

SD20-G Series
340
X Communication
10.1 Communication
Servo drive provides RS485 communication. The description below shows the communication wiring and
communication protocol.
10.1.1 MODBUS General
Modbus is a serial and asynchronous communication protocol. Modbus protocol is a general language applied
to PLC and other controlling units. This protocol has defined an information structure which can be identified
and used by a controlling unit regardless of whatever network they are transmitted.
You can read reference books or ask for the details of MODBUS from Parker..
Modbus protocol does not require a special interface while a typical physical interface is RS485.
10.1.2 MODBUS Protocol
1 Transmission mode
(1) ASCII 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
‘0’ ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’
ASCII Code 30H 31H 32H 33H 34H 35H 36H 37H
Characters
‘8’ ‘9’ ‘A’ ‘B’ ‘C’ ‘D’ ‘E’ ‘F’
ASCII Code 38H 39H 41H 42H 43H 44H 45H 46H
(2) RTU mode
In RTU mode, one Byte is expressed by hexadecimal format. For example, 31H is delivered to data packet.
2 Baud rate
Setting range: 2400, 4800, 9600, 19200, 38400, 57600
3 Frame structure:
(1) ASCII mode
Byte Function
1
7
0/1
1/2
Start Bit (Low Level)
Data Bit
Parity Check Bit (None for this bit in case of no checking. Otherwise 1 bit)
Stop Bit (1 bit in case of checking, otherwise 2 bits)
(2) RTU mode
Byte Function
1
8
0/1
1/2
Start Bit (Low Level)
Data Bit
Parity Check Bit (None for this bit in case of no checking. Otherwise 1 bit)
Stop Bit (1 bit in case of checking, otherwise 2 bits)
4 Error Check
(1) ASCII mode
Longitudinal Redundancy Check (LRC): It is performed on the ASCII message field contents excluding the
‘colon’ character that begins the message, and excluding the CRLF pair at the end of the message.