Siemens SIMATIC S7 System Manual page 346

Program instructions
7.13 Program control
LAD FBD
Input / output Data type
S_bit BOOL
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STL Description
LSCR S_bit The SCR instruction loads the SCR and logic stacks with the value of the
S bit referenced by the instruction.
The resulting value of the SCR stack either energizes or de-energizes the
SCR stack. The value of the SCR stack is copied to the top of the logic
stack so that LAD boxes or output coils can be tied directly to the left
SCRT S_bit
power rail and no preceding contact instruction is required.
CSCRE
The SCRT instruction identifies the SCR bit to be enabled (the next S_bit
to be set). When power flows to the coil or FBD box, the CPU turns on the
referenced S_bit and turns off the S_bit of the LSCR instruction (that ena-
bled this SCR segment).
SCRE
The CSCRE (conditional SCR end) instruction, for STL and FBD, termi-
nates execution of the SCR segment when enabled. For LAD, a condi-
tional contact placed before a SCRE coil performs the conditional SCR
end function.
The SCRE (unconditional SCR end) instruction, for STL and FBD, termi-
nates execution of the SCR segment. For LAD, an SCRE coil connected
directly to the power rail performs the unconditional SCR end function.
Operand
S
System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART