Writing Commands - Siemens SENTRON 3WA System Manual

• If the Modbus TCP whitelist is activated, the Modbus TCP connection must have
sufficiently high access rights in order to be able to write the parameter. You can find
more information on the Modbus TCP whitelist in Chapter Modbus TCP whitelist
(Page 39).
• If the parameter is protected by remote parameterization protection, remote
parameterization protection must be deactivated. You can find information on remote
parameterization protection in the 3WA Equipment Manual; see Chapter Reference
documents (Page 5).
With a Modbus function code 16 (hex 0x10) write frame, multiple parameters can also be
written provided the rules specified above are observed analogously. No gaps or unwritten
data points may appear between parameters.
Note
Parameters are identified as such in the Modbus register map.
5.3.2.3

Writing commands

Modbus function code 16 (hex: 0x10) writes commands in the 3WA air circuit breakers.
Commands with a length of one register can also be written using Modbus function
code 6 (hex: 0x06).
The following rules must be observed for a valid command:
• The start address of the frame must refer to the register address at the start of the
command.
• The command must be written in full.
• If commands do not contain an argument, 0x0815 must be transferred as a parameter
value on Modbus.
• The command must exist in the concrete 3WA system.
• If the Modbus TCP whitelist is activated, the Modbus TCP connection must have
sufficiently high access rights in order to be able to write the command. You can find
more information on the Modbus TCP whitelist in Chapter Modbus TCP whitelist
(Page 39).
• If the command is protected by remote parameterization protection or remote switching
protection, the relevant protection must be deactivated. You can find information on
remote parameterization protection and remote switching protection in the 3WA
Equipment Manual; see Chapter Reference documents (Page 5).
• Only one command may be written per frame.
Note
Commands are identified as such in the Modbus register map.
3WA Air Circuit Breaker Communication
System Manual, 11/2021, 92310000004-02
5.3 Function codes, metering values and parameters
Modbus TCP
37