Ladder Logic Bit Instructions – Part 2

4. Positive Transition or One Shot Rising (OSR) Edge

Positive Transition instruction becomes Logic high (State”1″) only for the moment, “Tagname” value transit from Logic low(0) to Logic High(1).

Note: The name Positive transition or OSR is depends on the PLC manufacturer.

Refer the following Examples,

The moment when Tagname transits from “0” to “1”, the Positive instruction gets activated and gives output Logic high as surge.

5. Negative Transition or One Shot Falling (OSR) Edge

Negative Transition instruction becomes Logic high(1) at the only moment when the Tagname value transit from Logic High(1) to Logic Low(0).

Refer the following Examples,

The moment when Tagname transits from “1” to “0”, the Negative instruction gets activated and gives output Logic high as surge.

6. Latched (Set) Coil & Unlatched (Reset) Coil

When the positive pulse or surge input is given to the Latched coil instruction, it gets activated and remains in the Logic high state until the same Tag resets by Unlatched or Reset instruction.

Refer the following example to understand the both Latched & Unlatched Instruction.

The following diagram is the example for Latch and Unlatch function using simple Contact and Coil instructions. This logic gives the same result as the above logic.