Function Code 23 (Read/Write Multiple Registers) - Siemens SIRIUS 3RW5 series Manual

7.2.7

Function Code 23 (Read/Write Multiple Registers)

This function enables the Modbus client system to write and read several registers from
3RW5 register memory area using a single function call.
Note
Read/Write Multiple Registers
With the FC 23, it is only possible to access the process image output (PIQ) and the process
image input (PII).
The write operation is the first executed operation here. This function is the typically used
function call for outputting cyclic data in the 3RW5 soft starter and for reading back inputs or
device statuses.
A valid address from the bit memory area is expected as the start address. The selected
address must be designated as writable in the data tables in chapter Data tables (Page 75).
Request telegram
Address Field
7 bytes
-
Start address write
operation
2 bytes
0x8200
Response telegram
Address Field
7 bytes
-
SIRIUS 3RW5 Modbus TCP communication module
Manual, 03/2018, A5E43676481002A/RS-AA/001
Function Code
1 byte
0x17
Number of registers N
(write access)
2 bytes
0x0001
Function Code
1 byte
0x17
Messages and diagnostics
Start address read
operation
2 bytes
0x8000
Number of bytes
(write access)
1 byte
0x01
Number of bytes N
1 byte
0x0010
7.2 Function Codes
Number of registers
(read access)
2 bytes
0x0008
Data (write access)
N x 2 bytes
0x0041
Data
N x 2 bytes
-
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