Appendix A. Modbus ProtocolC2000 Plus
A-3
(7, O, 1)
Odd
parity
Start
bit
01234
5
6
Stop
bit
7-data bits
10-bits character frame
11-bit character frame (For RTU):
(8, N, 2)
Start
bit
0
12
3456
Stop
bit
8-data bits
11-bits character frame
Stop
bit
7
(8, E, 1)
Start
bit
0
12
3456
Stop
bit
8-data bits
11-bits character frame
7
Even
parity
(8, O, 1)
Start
bit
01
2
3456
Stop
bit
8-data bits
11-bits character frame
7
Odd
parity
A-3 Communication Protocol
1. Communication data frame
ASCII mode:
STX Start character = ‘:’ (3AH)
Address High
Communication address:
one 8-bit address consists of 2 ASCII codes
Address Low
Function High
Command code:
one 8-bit command consists of 2 ASCII codes
Function Low
DATA (n-1)
Contents of data:
n x 8-bit data consists of 2n ASCII codes
n ≤ 16, maximum of 32 ASCII codes (20 sets of data)
…….
DATA 0
LRC Check High
LRC checksum:
one 8-bit checksum consists of 2 ASCII codes
LRC Check Low
END High
End characters:
END1= CR (0DH), END0= LF(0AH)
END Low