Safety Mechanisms
Fail-Safe Systems
A5E00085588-03
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3.9.2 Communication Between F-Run-Time Groups
Run-time groups that contain fail-safe blocks are referred to as F-run-time groups.
Data transmission between the F-run-time groups of a user program must be
safety-related. The fail-safe blocks F_S_BO, F_S_R and F_R_BO, F_R_R are
available for safety-related communication between F-run-time groups. This
enables you to transfer a fixed number of parameters of the same F-data type.
The following data types are supported: BOOL, REAL.
To permit communication between F-run-time groups in different cyclic interrupt
OBs, the cyclic interrupt with the shorter cycle must be configured with a higher
priority.
The F_S_BO (BOOL), F_S_R (REAL) blocks are integrated in the sending F-run-
time group, and its F input parameters are interconnected to the sending
parameters of other fail-safe blocks. The F_R_BO (BOOL), F_R_R (REAL) blocks
are inserted in the receiving F-run-time group, and its F output parameters are
interconnected to the inputs of other fail-safe blocks. The connection between
F_S_BO and F_R_BO or F_S_R and F_R_R is established by means of
interconnection in CFC.
The F_R_BO and F_R_R blocks have inputs to supply substitute values for the
ouptuts when a fault is detected (e.g. Timeout).
See Also
Programming Communication Between F Run-Time Groups Within a CPU
3.9.3 Communication Between the F-CPU and F-I/Os
Safety-Related Communication Between the F-CPU and F-I/Os Via PROFIsafe
The Safety Program communicates with the F-I/Os via PROFIsafe, the safety-
related bus profile of PROFIBUS DP/PA. This safety protocol is implemented in the
Safety Program in the F module driver blocks, as well as in the firmware of the F-
I/Os.
Safety-related communication between the Safety Program and the F-I/Os takes
place via cyclic user data transfer. An important parameter for this is the monitoring
time specified during configuration of the F-I/Os and automatically passed to the
F
module driver blocks as an
input parameter.
Non Safety-Related Communication Between the F-CPU and F-I/Os
For non safety-related communication between the F-CPU and the F-I/Os, the
usual mechanisms - direct access, access to process image or records - can be
used. For example, non-safety-relevant diagnostic information is transferred
acyclically from the F-I/Os by means of record transfers.
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