RS485 Interface (For Link Model of 19073 + RS485)
5-3
5.4
Communication Protocol
This interface uses half duplex of 2-wire system non-synchronized transmission mode.
Before the bus control is transferred, please wait the time of two characters.
The transmission format of character is 1 initial bit, 8 data bits and 1 end bit, the total is 10
bits.
The receivers don’t respond any data under broadcast mode. When the receivers receive
the query functions under node-to-node transmission mode, it returns the relative data.
However, the receivers receive the execution command, it returns the result of executing.
About Reply Message, please refer the descriptions of command.
The commands are packed into packets, Data Frame as the following:
Header
DA
SA
Length
Data Field
Checksum
1 byte
1 byte
1 byte
1 byte
n bytes
1 byte
Header:
0xAB
Destination Address: 0x0 ~ 0x7F, 0xFF is broadcast address
Source Address:
0x0 ~ 0x7F
Data Field Length:
It means the length of data field.
Data Field:
Please refer the command set.
Command Code
Parameter
1 byte
0 ~ n-1 bytes
Checksum: Summing these values into two’s complements, included data are DA + SA +
Data Field
Slave 1
Slave n
Master
Master
n1 Bytes
Slave1
2 Bytes
n2 Bytes
Master
2 Bytes
n3 Bytes
2 Bytes
Slave n
n4 Bytes
START
0
1
2
3
4
5
6
7
STOP