Communication Options
3.6 Safety-Related CPU-CPU Communication
Safety Engineering in SIMATIC S7
System Manual, 04/2006, A5E00109529-05
3-15
3.6.2
S7 Distributed Safety: Safety-related Master-I-Slave Communication
Introduction
In S7 Distributed Safety, safety-related CPU-CPU communication between the safety
program of the F-CPU for the DP master and the safety program(s) of the F-CPU(s) for one
or more I-slaves takes place over master-slave connections, as in standard systems.
Communication Overview
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S7 Distributed Safety: Safety-related master-I-slave communication
Master-I-Slave Communication
Safety-related communication takes place with the aid of two fail-safe application blocks: the
F_SENDDP block for sending data and the F_RCVDP block for receiving data. These blocks
are called by the user in the respective safety program of the F-CPU. They can be used to
transfer a fixed number of fail-safe data of data types BOOL and INT in a fail-safe manner.
Required User Steps
The user should carry out the following steps for safety-related master-I-slave
communication:
1. Configure I-slave in
HW Config
2. Configure the DP master system in
HW Config
3. Connect the I-slave to the DP master
4. Set the address areas for data exchange in
HW Config
5. Call F_SENDDP and F_RCVDP from the
Distributed Safety F-library in the safety
programs of the F-CPU for the DP master and I-slave
6. Assign parameters for F_SENDDPs and F_RCVDPs
7. Once the safety programs have been created, compile and download them to the
appropriate F-CPU.
