Modbus Flag Bits

[adambutt]

I have a piece of OEM equipment that stores all boolean values in Modbus holding registers using bit flags. Is there a way to configure the periphery address for a database bool to read a specific bit of a word? The only alternative I can think of is to read in the word as an integer and use a scrip to extract the necessary bit and write that out to a boolean in the database. Are there any better or recommended solutions for this?

Thank you for your help.

[Gertjan van Schijndel]

You can specify a subindex in the address config to read a single bit from a word.

[fmulder]

Translating a word into bits can be done via a dp function but this has a mayor disadvantage. The problem is that the quality is not taken into account.
When you pull the cable to the PLC then the word will become 'bad' but the bits will still remain 'good' !!

In general, use the subindex when possible

[adambutt]

I tried using the subindex to select the bit I want, but I get an error indicating that I can only use polling with a subindex of 0. If I can't put this address in a polling group, how will it update?

Thanks.