STEP7 Communication blocks

Hi,

Normally I don't work with STEP7, so it is possible that my question a stupid one is.

The communication blocks in the libraries for what do you use them.
I read the helpfiles of the blocks and distracted you use them for Profibus DP.

Now I'm confused because you don't need them to send data over the profibusnetwork, I already test that. So what is the purpose of the communication blocks?

Thx

You will need them if you exhcange data between eg. two PLC:s.

You will also need them if you have eg. a drive that you have to read more them 4 word at ones (consistency check over total lenght).

communications blocks

Hi Niklas,

Thx for the respons, so if I understanding correct, you use the blocks only if you have 2 or more PLC with CPU's or you want to send data longer than 2DW in one time to a drive. And using profibus for the connection between the plc's and the drives

When you use Profibus master and profibus slaves you don't need them, correct?

Greeting

The max amount is 4 dw it´s a double word eg. load OD 1 (outdouble)
Usually/always the drive is a Profibus slave.
You also use the communication blocks if you have other "smart" slaves that require more data then 1DW eg. encoders.

There are quite a number of comms block in step7 for different protocol: MPI. profibus, FDL, ethernet etc. You would always require them unless in the hardware configuration the IO addresses are already assigned. You would definitely required them for Data Blocks.
Could you elaborate more on your problems?