Hello SIOS forum community.

The communication between redundant and non-redundant controllers usually requires the parallel handling of two communication connections on the non-redundant side, i.e. one connection to each CPU of the R/H system.

In connection with S7-1500R/H controllers an alternative and simple method is available to solve this task. The two CPUs of a S7-1500R/H station can be assigned during the project engineering for each interface additionally to the respective individual IP addresses a common IP address. This so called "System IP" represents the whole station and is served by the "Primary-CPU*".

(*the CPU that has just assumed the leading role in the CPU pair at runtime is referred to as the "Primary CPU").

A communication partner such as a non-redundant controller can thus connect to the system IP** and is always connected to the S7-1500R/H system via this, regardless of which CPU has just assumed the primary role.

A perfect combination forms this technology in connection with the operation of the non-redundant controller at the MRP ring at the x1 interface of the R/H CPUs, since here also the line path to the primary CPU is redundant at any time.

(**the connection types of the programmed "Open user communication" are available here).

If another communication partner is connected to the x2 interface, which does not have an onboard switch and therefore cannot be directly integrated into an MRP ring, at least a small part of the connection path to the primary CPU remains non-redundant (e.g. the patch cable to the next switch). If this restriction should not be tolerable, a double connection starting from the non-redundant partner would then have to be implemented here again.

Another very simple and effective method is to use a PROFINET PN/PN coupler. This is integrated into the MRP ring and communicates with the R/H system as a PROFINET IO device. Since the PN/PN coupler supports PROFINET S2 redundancy, it can switch "bumplessly" between the two redundant PROFINET IO controllers (i.e. the pair of R/H CPUs) and benefits from the path redundancy of the PROFINET MRP ring.

On the second side, the PN/PN coupler acts as a simple PROFINET IO device under the non-redundant controller. Thus, on the non-redundant side no additional measures are required for the communication with the redundant partner, while on the R/H system side a fully redundant connection is provided.

Best regards,

SIMATIC International Technical Support Hub