OSF (One Shot Falling) Ladder Logic Instruction


Ladder logic output instruction that writes bit data to a referenced Storage Bit and an Output Bit. The Output Bit is set or cleared depending on the Storage Bit. The instruction sets the Storage Bit if the preceding logic is true and clears it when false. The Output Bit is set for one program scan when the Storage bit is cleared.  The Storage Bit is cleared when the preceding logic is false. This instruction provides a one shot output bit, triggered when the preceding logic transitions from true to false. The OSR (One Shot Rising) bit provides the one shot output bit when the preceding logic is true.

List of arguments

BOOL TAG           Storage Bit

BOOL TAG           Output Bit

Important Note: Do not reference a Boolean tag to more than one OSF instruction.