Siemens SIMATIC S7 F Manual page 341

Block
Name
F_TESTM
F_TI_FTI
F_TOF
F_TON
F_TP
F_XOR2
F_XOUTY
DB_INIT*
DB_RES*
FAIL_MSG*
RTG_LOGIC*
* Even though these blocks aren't yellow, they are safety critical and are placed
automatically by the CFC editor. The user may not place or remove these blocks.
Changes are not permitted except for connections to the F_SHUTDN block (see
the F_SHUTDN block description in the Fail-Safe Block section for further
description).
Newly created accepted F block types can be added to the list of certified F-Blocks.
Fail-Safe Systems
A5E00085588-03
Block Function
Number
FB 400 Switching of Safety Mode on and off
FB 368 Converts from TIME to F_TIME
FB 344 Timer off-delay
FB 343 Timer on-delay
FB 342 Timer pulse
FB 303 XOR logic operation on two inputs
FB 306 Binary selection X out of Y
FC 180 F-run-time group coldstart initialization logic
FC 301 Supports the startup characteristics in the
event of a cold restart/warm restart of the
CPU
FC 181 F-run-time group shutdown diagnostic error
reporting
FB 459 F-run-time group shutdown and restart logic
interface
Check Lists
Check
A-9