Exiting An F-Stop; F Startup And (Re)Start Protection; F-Startup - Siemens SIMATIC PCS 7 Operating Manual

Configuring the safety program

7.5 F startup and (re)start protection

Error in both F CPUs:
The safety program goes into F-STOP immediately.
7.4.6

Exiting an F-STOP

Run an F-startup as described in the following chapter.
7.5 F startup and (re)start protection
7.5.1

F-startup

S7 F-systems do not make a distinction between a CPU cold restart and a CPU warm
restart. The F_CHG_BO, F_CHG_R (part of the Safety Data Write function), and F_MOV_R
(S7 F-Systems Lib V1_3 and higher) F-blocks are exceptions to this rule.
Both a CPU cold restart and a CPU warm restart will generate an F-startup. With an F-
startup, the safety program launches automatically with the initial values.
An F-startup is performed:
● After a CPU STOP, when you perform an F-CPU warm restart
● After an F-STOP, when the "F_SHUTDN" F-block detects a positive edge at the
RESTART input
Following a partial shutdown of the safety program, only the F-shutdown groups involved
in the F-STOP perform an F-startup. F shutdown groups with errors remain in F-STOP.
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Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB