SD710 Series Servo Drive User Manal Chapter 11 Communication
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11.1 485 communication
The servo drive's master computer communication uses a standard Modbus protocol based on the 485 interface.
Modbus is a serial, asynchronous communication protocol and a common language for its application to PLCs or other
controllers. This protocol defines a message structure that a controller can recognize as being in use, regardless of the
network over which they are transmitted. The Modbus protocol does not require a dedicated interface; the typical physical
interface is RS485.
11.1.1 Modbus communication protocol
(1) Transmission mode
The transmission modes are divided into ASCII transmission mode and RTU mode.
This product supports RTU mode only. The characters sent in RTU mode are expressed as hexadecimal numbers. For
example, if you send 30H, you can directly input 30H into the packet.
(2) Baud rate
Setting range: 4800bps, 9600bps, 19200bps, 38400bps, 57600bps, 115200bps.
(3) Data frame format
The data frame format for RTU mode is as follows.
Table 11-1 RTU Data Frame Format
Start bit position
address
command
data
CRC check
Stop bit
T1-T2-T3-T4
1 byte
1 byte
N bytes
2 bytes
T1-T2-T3-T4
(4) 03H command code reads N consecutive words
Function: Read N words (Word), up to 16 words in a row.
For example, 2 words are read continuously from the start address E003H of servo drive with the station number 01H.
The command message and response message are as follows.
Table 11-2 0x03 Command Format
Command message (master)
Response message (slave)
Address
01H
Address
01H
Command
03H
Command
03H
Start data address
E0H (high byte)
Number of data
(in byte)
04H
03H (low byte)
Number of date
(in word)
00H
Start data address
0004H low 16 bits
3AH
02H
9AH
CRC check (low)
03H
Start data address
0004H high 16 bits
00H
CRC check (high)
CBH
05H
-
-
CRC check (low)
16H
-
-
CRC check (high)
C7H
