Inovance MD290T45G/55P - Page 219

7. Interfaces and Communication
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7
7.5.3 Data Format
The drive supports reading and writing of word-type parameters only. Reading command is 0x03
and writing command is 0x06. It does not support reading and writing of bytes or bits.
The Modbu-RTU protocol communication data format of the drive is as follows:
Master sending 1 Slave response 1 Master sending 2 Slave response 2
Interval of at
least 3.5-byte
time
Interval of at
least 3.5-byte
time
Data frame
Data frame
A
B
In theory, host computer can read several consecutive parameters (n can reach up to 12) but the
last parameter it reads must not jump to the next parameter group. Otherwise, an error occurs on
response.
Function code
H----L
CRC and
L----H
Idle
Frame of reading
response from
the slave
1 byte 1 byte (2n) byte1 byte 2 byte> 3.5 byte
Calculate CRC
Idle (frame header)
Read
command
0x03
Target
station
address
Number
of bytes
(2n)
Parameter
address
H----L
Function
parameter
H----L
CRC and
L----H
Idle
Frame of writing
command from
the master
Idle (frame header)
1 byte 1 byte 2 byte 2 byte> 3.5 byte 2 byte
Calculate CRC
Target
station
address
Write
command
0x06
Parameter
address
H----L
Function
parameter
H----L
CRC and
L----H
Idle
Idle (frame header)
1 byte 1 byte 2 byte 2 byte> 3.5 byte 2 byte
Calculate CRC
Target
station
address
Write
command
0x06
Frame of writing
response from
the slave
If the slave detects a communication frame error or reading/writing failure is caused by other
reasons, an error frame will be returned as follows:
0x83
Error
type
CRC and
L----H
Idle
Frame of reading
response error from
the slave
Idle (frame header)
1 byte 1 byte> 3.5 byte 2 byte
Calculate CRC
1 byte
0x86
Error
type
CRC and
L----H
Idle
Frame of writing
response error from
the slave
1Byte 1Byte>3.5Byte 2Byte
Calculate CRC
1Byte
Error type:
01: Command code error
02: Address error
03: Data error
04: Command cannot be handled
Idle (frame header)
Target
station
address
Target
station
address