Stl Logic Stack Instructions - Siemens SIMATIC S7 System Manual

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Program instructions

7.1 Bit logic

STL logic stack instructions

The AND Load instruction (ALD) combines the values in the first and second levels of the stack using a logical

AND operation. The result is loaded in the top of stack. After the ALD is executed, the stack depth is decreased

The OR Load instruction (OLD) combines the values in the first and second levels of the stack, using a logical

OR operation. The result is loaded in the top of the stack. After the OLD is executed, the stack depth is de-

creased by one.

The Logic Push instruction (LPS) duplicates the top value on the stack and pushes this value onto the stack.

The bottom of the stack is pushed off and lost.

The Logic Read instruction (LRD) copies the second stack value to the top of stack. The stack is not pushed or

popped, but the old top-of-stack value is destroyed by the copy.

The Logic Pop instruction (LPP) pops one value off of the stack. The second stack value becomes the new top

of stack value.

The Load Stack instruction (LDS) duplicates the stack bit (N) on the stack and places this value on top of the

stack. The bottom of the stack is pushed off and lost.

AENO is used in the STL representation of the LAD/FBD box ENO bit. AENO performs a logical AND of the

ENO bit with the top of stack for the same effect as the ENO bit of a LAD/FBD box. The result of the AND op-

eration is the new top of stack.

Not applicable for LAD or FBD

LDS (Load Stack) Input

Constant (0 to 31)

System Manual, V2.3, 07/2017, A5E03822230-AF

S7-200 SMART

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