PLC Programming Fundamentals – OTL Instruction

The OTL, also known as the Output Latch, instruction will force a single bit of logic into a high state if all the conditions leading to it are true. It’s a basic instruction which is powerful but can cause programmers a lot of grief if used improperly or too frequently. This instruction is found on the right side of a ladder logic rung and will switch a bit to a HIGH state once it executes. Unlike the OTE Instruction, the OTL will never turn the bit LOW. In order to make that happen, you can leverage other instructions which accomplish exactly that. That being said, the most common pairing with an OTL is an OTU (Output Unlatch).

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