Latch & Unlatch Question

Thread Starter


Joined Mar 18, 2020
Why does pressing unlatch first doesn't energize latch, but pressing latch secondary lights both latch and unlatch?
1586464944642.png Why does pressing the input A light-up latch and unlatch buttons at the same time? Pressing Input b unlatches
Last edited:

Delta prime

Joined Nov 15, 2019
Here you go!
The output latch (OTL) instruction is a retentive output instruction that is used to maintain, or latch, an output. If this output is turned on, it will stay on even if the status of the output logic that caused the output to energize becomes false. The OTL instruction remains in a latched on condition until an unlatch instruction (OTU) with the same referenced tag is energized. The output latches are used in programs where the value of the output is maintained constant even if the plant shut down due to power failure.

  • The OTL instruction will write a 1 to its address when true.
  • When the OTL goes false, the output address will remain a 1.
  • This is true even if the processor powers down and
    then back up.
  • The output address will remain a 1 until reset to 0 by the unlatch instruction.
  • If the output address is off, both the latch and unlatch instructions are not intensified, but once the bit is turned on, you will see both the latch and unlatch intensified even though both inputs are shut off.