Hi,

Can we connect 4 -300CPU in profinet communication?

Is it mandatory to go with PN/PN coupler and CP cards?

Hi,

no, it´s not necessary to use CP/Coupler.

You can use the integrated PN-Interface of the PLC (if there is only DP/MPI, you need a CP).

Please check the following manual:

CPU-CPU communication with SIMATIC controllers (compendium)

On page 95 you will find some informations how to communicate between S7-300.

Regards,

Towome