102
ASCII mode
name
meaning
instruction
Start
Communication began
The starting character ':' (ASCII: 3 ah)
Address
The communication address
Address, that is, drive site number.
For example:
a drive site # 32, hexadecimal for
20 h, Address = '2', '0' or '2' = 32 h,
'0' = 30 h
CMD
order
1 byte contains two ASCII.
Commonly used
commands: 3 h (read registers), 6
h ((reading a single register), 8 h
(diagnostic function), 10 h (write
multiple register)
DATA(n-1)
The data content
N = 2 N
word bytes = 4 N
ASCII (N < = 8)
⋯⋯
DATA(0)
LRC
Check code
1 byte contains two ASCII
End 1
The end of the code 1
0 dh, i.e., CR
End 0
The end of the code 0
0 ah, that is, LF
RTU mode
name
meaning
instruction
Start
Communication began
The rest time to at least 3.5
bytes transmission time
Address
The communication address
