Modbus
SECTION 5 Modbus Communications Procedure
5-4
■ Response Frame
● Normal Response Frame
● Error Response Frame
Slave address
The number specified in the command frame is entered as-is.
This is the unit number of the Unit returning the response.
Function code
This is the received function code with the hexadecimal value
of H’80 added to indicate that the response is an error
response.
Example: Received function code = H’03
Function code in response frame when an error occurred =
H’83
Error code This code indicates the kind of error that occurred.
CRC-16
Cyclical Redundancy Check
This check code is calculated with the data from the slave
address to the end of the data.
The check code is 2-byte hexadecimal.
CRC-16
11
Data
CRC-16 calculation range
2 bytes
Slave
address
Function
code
CRC-16
111
CRC-16 calculation range
2 bytes
Slave
address
Function
code
Error
code
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