Mitsubishi Electric MELSEC iQ-RJ71C24-R4 - Read;Write Multiple Registers (FC: 17 H)

3 MODBUS STANDARD FUNCTION DETAILS
3.17 Read/Write Multiple Registers (FC: 17H)
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3.17 Read/Write Multiple Registers (FC: 17H)
Operation description
Reads/writes data from/to multiple holding register areas.
During the processing, writing is performed first, followed by reading.
Request message format (from master to slave)
Ensure that the specified number of write points matches the number of bits specified with the number of
bytes.
Response message format (from slave to master)
■ When completed successfully
■ When completed with an error
(H) (L)
17H
(H) (L) (H) (L) (H) (L) (H) (L)(H) (L)
Data
Read start holding
register number
Function code
Number of read points
n
Write start holding
register number
Number of bytes m×2
Number of write points
m
Number of
bytes m×2
Write device data 1 Write device data m
(0000H to FFFFH)
(00H to F2H)
(0001H to 0079H)(0000H to FFFFH)(0001H to 007DH)
(H) (L)
17H
(H) (L)
Read device data 1
DataFunction code
Number of bytes
n×2
Read device data n
Number of bytes n×2
97H
Data
Exception code
Function code