Pilz PSS SB FT, Basic license - Manual (Page 54)

6-10 Modular Block System: Burner Management
Standard Function Blocks SB149
With spurious signals:
If a step enabling condition is met at the COND input, it will not
cause the outputs to set too early.
Only if the step block was activated with RDY = 1 do the
outputs react to the step enabling condition.
Repeated “1”-Signals at the COND input do
not cause malfunctions further on in the
process.
The RDY output may not be set a second time after the step
block has been run through once.
Therefore, in the FS program it must be monitored that only one
individual
NEXT output is active and all other NEXT outputs
have a “0”-Signal. Should it be detected that more than one
NEXT output has a “1”-Signal, an immediate fault lockout