Mitsubishi Electronics FX1S manual 20 End, Program scan

FX Series Programmable Controllers Basic Program Instructions 2

2.20End

FX1S FX1N FX2N FX2NC

Mnemonic	Function	Format		Devices	Program steps
END	Forces the current
	program scan to		END	N/A	1
(END)
	end

Basic points to remember:

-Placing an END instruction in a program forces that program to end the current scan and carry out the updating processes for both inputs and outputs.

-Inserting END instructions in the middle of the program helps program debugging as the section after the END instruction is disabled and isolated from the area that is being checked. Remember to delete the END instructions from the blocks which have already been checked.

-When the END instruction is processed the PLCs watchdog timer is automatically refreshed.

A program scan:

• A program scan is a single processing of the loaded program from start to finish, This includes updating all inputs, outputs and watchdog timers. The time period for one such process to occur is called the scan time. This will be dependent upon program length and complexity. Immediately the current scan is completed the next scan begins. The whole process is a continuous cycle. Updating of inputs takes place at the beginning of each scan while all outputs are updated at the end of the scan.

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