TRB 145 modbus single bit request

[baldomax]

Hi to everyone,
I’m trying to read some modbus registers from a board and the communication
works well . My problem is that I need to read a single bit of a register .
For example I need to read only the bit 9 of the 16 bit register 11160.

Can someone help me how to make request?

Thank you

Massimo

[anon65719490]

Hello,

Unfortunately, it won’t be possible to directly query a single bit within a 16-bit Modbus register. The Modbus protocol itself doesn’t support addressing individual bits inside a holding register or input register; it only allows reading the entire 16-bit value.

If your device supports it, individual bits can be addressed via coils or discrete Inputs, but not within a register.

A common approach is to read the full register value and then use bitwise operations on the received data to check the specific bit you need on the client side.

Best regards.