modbusTCP with with CPU315-2PN/DP

Hello,

    I am using openmodbus TCP communication with CPU315-2PN/DP with reference to the document

https://cache.industry.siemens.com/dl/files/304/22660304/att_57060/v1/modbustcppncpu_en.pdf

As per document, A maximum of 125 registers is possible for reading functions per message frame for Holding and Input Register. A maximum of 2000 bits is possible for Coils and Inputs.

In my application, i need to read  more than 125 register, presently 164 holding registers and it may increase later.

How i can read 164 holding register from the modbusTCP device?

Thank you

Hello,

you need do some state machine in your code to differ 2 independed requests, one for first able number of registers and next for rest of number amount devices. You can split both requests to numbers what is best for you to have good results. As example, you can read f.ex. for first 100 registers and at second request 64 registers.