Code 06 - Write A Single Register; Figure 2-16 Write A Single Register Example - Request; Figure 2-17 Write A Single Register Example - Response - Siemens SIMATIC TI505 User Manual

Modbus Function Descriptions (continued)
Code 06 — Write a
Single Register
WARNING
!
2-16 Modbus Commands
Code 06 allows the contents of a holding register to be changed. Addressing
is sequential up to the maximum memory size for a particular PLC. This
function is limited to integer values contained in V-memory. The MODNIM
will also direct any broadcast address (00) to all attached secondaries.
[This command is comparable to a TIWAY I request using Primitive 30 and
TT-type 01 (Variable memory)].
Because of differences in memory mapping between Modbus PLCs
and SIMATIC TI PLCs, you should be quite certain of the effects of
the broadcast command before issuing it.
Example:
Request: 07 06 0064 0220 XXXX
Figure 2-16 Write a Single Register Example — Request
This request to secondary 7 is asking for the value of holding register 0064
(100 decimal) to be changed to 0220 (544 decimal).
Response: 07 06 0064 0220 XXXX
Figure 2-17 Write a Single Register Example — Response
The response to Function Code 06 is to return the request as received. In
the case of a broadcast request, there is no response.
Checksum (XXXX)
Data value (0220)
Register address (0064)
Function code (06)
Slave address (07)
Checksum (XXXX)
Data value (0220)
Register address (0064)
Function code (06)
Slave address (07)
SIMATIC TI505/TI500 MODNIM User Manual