Different design versions can be implemented according to requirements. These are illustrated below using the example of ET 200M distributed I/O:

Single-channel, one-sided I/O for S7-400F

The plant requires a safety-related controller. Fault tolerance is not required. The following are required:

• 1 CPU S7‑400H with F‑Runtime license
• 1 PROFIBUS DP or PROFINET line
• ET 200M with IM 153‑2 (PB DP) or IM 153‑4 (PN)
• Safety-related signal modules in non-redundant design.

In the event of a fault, the I/O is no longer available. The safety-related signal modules are passivated.

Single-channel, switched I/O for S7-400FH

The plant requires a safety-related controller. Fault tolerance is required on the CPU side. The following are required:

• 2 CPU S7‑400H with F-Runtime license.
• 2 PROFIBUS DP lines.
• 1 ET 200M with 2 IM 153-2 (redundant).
• Safety-related signal modules in non-redundant design.

If the CPU, IM 153-2 or PROFIBUS DP line fails, the controller remains available. Failure of the safety-related signal modules or the ET 200M station means the I/O is no longer available. The safety-related signal modules are passivated.

Redundant, switched I/O for S7-400FH

The plant requires a safety-related controller. Fault tolerance is required on the CPU side and the I/O side. The following are required:

• 2 CPU S7‑400H with F-Runtime license.
• 2 PROFIBUS DP lines.
• 2 ET 200M with 2 IM 153-2 (redundant).
• Redundant version, safety-related signal modules.

In the event of failure of the CPU, IM 153-2, PROFIBUS DP line, safety-related signal modules or ET 200M station, the controller remains available.

Communication

Standard and safety-related communication between the central controller and the ET 200M takes place via PROFIBUS DP or PROFINET. The PROFIsafe profile specially developed for safety-related communication supports the transfer of user data for the safety functions within the standard data message frame. Additional hardware components such as special safety buses are not required. The necessary software is either integrated in the hardware components as an expansion of the operating system or loaded into the CPU later as a certified software block.