Xinje XD5 - Modbus Data Format; Modbus Transmission Mode; Modbus-RTU Data Structure; RTU Mode

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6-2-4 Modbus data format
Modbus transmission mode:
There are two transmission modes: RTU and ASCII; It defines serial transmission of bit
content in message domain; it decides how information to pack and decode; transmission
mode (and port parameters) of all devices in Modbus serial links should be the same.
Modbus-RTU data structure
RTU mode:
Under Modbus RTU (remote terminal unit) mode, message has two 4-bit hexadecimal
characters in every 8-bit byte. This mode has very high data density, higher throughput rate
than Modbus ASCII. Every message should be sent by continuous characters.
RTU mode frame check domain: cycle redundancy check（CRC）.
RTU mode frame description:
Modbus
station
Function
code
data
CRC
1 byte
1 byte
0~252 byte
2 byte
CRC low
CRC
high
Format:
START
No input signal ≧ 10ms
Address（station no.）
Communication address: 8-bit binary
Function
Function code：8-bit binary
DATA（n - 1）
Data content：
N*8-bit data, N≤8, max 8 bytes
……
DATA 0
CRC CHK Low
CRC check code
CRC CHK High
16-bit CRC check code is consist of two 8-
bit binary
END
No input signal ≧ 10ms
2. Modbus address：
00H：All the Xinje XC series PLC broadcast—— slave stations don’t response.
01H：Communicate with address 01H PLC.
0FH：Communicate with address 15H PLC.
10H：Communicate with address 16H PLC and so on. Up to 254（FEH）.
3. Function and DATA:
Function
code
Function
Modbus instruction
01H
Read coil
COLR
02H
Read input coil
INPR(not support Xinje PLC)
03H
Read register
REGR
04H
Read input register
INRR
05H
Write coil
COLW
06H
Write register
REGW
10H
Write multi-
register
MRGW