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FX Series Programmable Controllers Basic Program Instructions 2
2-23
2.20 End
Basic points to remember:
-Placin
g
an END instruction in a pro
g
ram forces that pro
g
ram to end the current scan and
carr
y
out the updatin
g
processes for both inputs and outputs.
- Insertin
g
END instructions in the middle of the pro
g
ram helps pro
g
ram debu
gg
in
g
as the
section after the END instruction is disabled and isolated from the area that is bein
g
checked. Remember to delete the END instructions from the blocks which have alread
y
been checked.
- When the END instruction is processed the PCs watchdo
g
timer is automaticall
y
refreshed.
Mnemonic Function Format Devices Program steps
END
(END)
Forces the current
pro
g
ram scan to
end
N/A 1
END
A program scan:
•A pro
g
ram scan is a sin
g
le processin
g
of the loaded pro
g
ram from start to finish, This
includes updatin
g
all inputs, outputs and watchdo
g
timers. The time period for one
such process to occur is called the scan time. This will be dependent upon pro
g
ram
len
g
th and complexit
y
. Immediatel
y
the current scan is completed the next scan
be
g
ins. The whole process is a continuous c
y
cle. Updatin
g
of inputs takes place at
the be
g
innin
g
of each scan while all outputs are updated at the end of the scan.