The PROFIsafe profile allows safety-related communication between the automation system (controller) and the process I/O via either PROFIBUS or PROFINET. The decision for choosing either PROFINET IO or the PROFIBUS DP/PA fieldbuses has a significant influence on the architecture of the safety-related system.

Safety-related design versions with PROFIBUS

In the case of a safety-related system with PROFIBUS communication integrated into SIMATIC PCS 7, a distinction is made across all architecture levels between two design versions:

• Single-channel, non-redundant design
• Redundant, fault-tolerant design

Both design versions are extremely variable, and offer a large scope for different customer requirements. Standard automation (basic process control) and safety-related functions can be combined flexibly, not only in the area of distributed I/O. Even at the controller level, they can be combined in one system or separated. In addition, there are numerous possibilities arising from the use of flexible modular redundancy.

Safety-related design versions with PROFIBUS

At the individual architectural levels (controller, fieldbus, I/O), you have the configuration alternatives shown in the figure in line with the I/O used (ET 200M, ET 200iSP, ET 200pro remote I/O stations or PROFIBUS PA devices with PA profile 3.0 or higher).

Safety-related design versions with PROFINET

Safety-related AS single stations (F systems) and AS redundancy stations (FH systems) from the S7‑400 range can be networked simply and effectively with ET 200M remote I/O stations via PROFINET IO. The PN/IE interface integrated in the CPU is available for this on the side of the automation systems, and the IM 153‑4 PN High Feature interface module in the ET 200M remote I/O stations.

The availability of the I/O devices on an AS Single Station (F systems) can be increased by a ring topology with media redundancy. If the transmission link in the ring is interrupted at one point, for example, due to a break in the ring cable or the failure of a station, the redundancy manager then immediately activates the alternative communication path.

Safety-related PROFINET IO communication with media redundancy

The maximum availability with minimum error handling times is achieved by the AS Redundancy Station (FH system) in conjunction with the system redundancy of the I/O devices. System redundancy refers to a type of PROFINET IO communication where each I/O device establishes a communication connection to each of the two CPUs of an AS Redundancy Station over the topological network. In contrast to the single-sided I/O device connection to only one CPU, failure of a CPU in this case does not automatically lead to failure of the connected I/O devices.

Safety-related PROFINET IO communication with system redundancy