This video goes over the Modicon 984 SUB instruction.
This instruction is used for many operations beyond simply the subtraction math operation because the instruction is very low cost to the processor, and is therefore very fast to execute.
The SUB is often used as a "Copy" instruction, as well as to decide if a value is greater than, equal to, or less than another value.
This was a requested topic, if you want to ask about something Modicon or Allen Bradley related (500, 5000, Studio, View Studio, etc) put it in the comments section.
