Positive, Negative Transition Bit Logic

Inputs/Outputs Operands Data Types
IN (FBD) I, Q, M, SM, T, C, V, S, L, Power Flow BOOL
OUT (FBD) I, Q, M, SM, T, C, V, S, L, Power Flow BOOL

Memory Ranges ENO Errors Instruction Support for S7-200 CPUs SIMATIC/International Mnemonics
The Positive Transition contact allows power to flow for one scan for each off-to-on transition.

The Negative Transition contact allows power to flow for one scan for each on-to-off transition.

In LAD, the Positive and Negative Transition instructions are represented by contacts.

In FBD, the instructions are represented by the P and N boxes.

In STL, the Positive Transition contact is represented by the Edge Up instruction. Upon detection of a 0-to-1 transition in the value on the top of the stack, the top of the stack value is set to 1; otherwise, it is set to 0.

In STL, the Negative Transition contact is represented by the Edge Down instruction. Upon detection of a 1-to-0 transition in the value on the top of the stack, the top of the stack value is set to 1; otherwise, it is set to 0.


Example