LOGO modbus write input register

Hi, 

need some help as I’m new to LOGO, I need to write to a modbus device input register. The register I need to write into is 406000. Seen some posts saying this can’t be done, could someone clear this up or instruct on how it can be done 

Hi, 

yes the modbus device is a gas analyser and i am changing the stream of which the analyser is reading. this can be done currently in a scada programme by manually inputting 1-3 and sending to S40600 (float, see attached picture) i am then also able to read the values for example on S403144 throught the scada programme. 

the only part i am looking to automate is the sending of 1-3 to 406000 but not sure how to write or comminucate this to the analyser. 

>The register I need to write into is 406000

The info below is generic Modbus information that applies to all Modbus implementations, it is not Siemens specific.

The leading numeral 4, (4)0600, indicates that the register is a Holding Register, not an Input Register (input registers start with the numeral (3)..

By Modbus Spec definition, an Input Register is Read-Only, while a Holding Register is always a read register and can be a write register if the device's firmware allows a write to that register.  Usually the device's documentation states whether the register is Read-only or R-W, read-write.

The Modbus Read instruction for Holding registers is Function Code 03.

The Modbus Write instruction to write to a single Holding register(s) is Function Code 06,

The Modbus Write instruction to write to multiple, contiguous Holding registers, use Function Code 16 (decimal) or 10 (hex).

Presumably register (4)0600 is a read/write register if that what's needed.