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FX Series Programmable Controllers Points Of Technique 10
10-2
10.3 Using The Forced RUN/STOP Flags
10.3.1 A RUN/STOP push button configuration
The FX pro
g
rammable controller has a sin
g
le RUN terminal. When power is applied to this
terminal the PLC chan
g
es into a RUN state, i.e. the pro
g
ram contained is executed.
Consequentl
y
when there is no power 'on' the RUN terminal the PLC is in a STOP state.
This feature can be utilized to provide the FX PLC with an external RUN/STOP - push button
control. The followin
g
PLC wirin
g
and pro
g
ram addition are required.
Explanation:
Pressin
g
the RUN push button sets the PLC into the RUN state. This means M8000 is ON.
Followin
g
the pro
g
ram, M8000 activates both M8035 and M8036. These two special auxiliar
y
devices set the PLC in to forced RUN mode. Releasin
g
the RUN push button would normall
y
return the PLC to the STOP state, but because the two auxiliar
y
coils, M8035 and 36 are ON,
the PLC remains in RUN. To stop the, PLC pressin
g
the STOP push button drives an input ON
and consequentl
y
M8037 turns ON. This then automaticall
y
forces OFF both M8035 and 36
and resets itself. Hence, the PLC is in its STOP status and awaits the c
y
cle to be
g
in a
g
ain.
Input priority:
• The STOP input is onl
y
processed after the pro
g
rams END statement has been reached -
this is because the ph
y
sical input used, i.e. an X device is normall
y
updated and processed
at that time. Therefor, the RUN input is
g
iven priorit
y
when both RUN and STOP inputs are
g
iven simultaneousl
y
.
•To
g
ive priorit
y
to the STOP input and provide a 'safer' s
y
stem, some form of mechanical/
circuitr
y
interlock should be constructed between both RUN and STOP inputs. A ver
y
simple example is shown in the wirin
g
dia
g
ram above.
• For push-button control to operate correctl
y
, the user must set the RUN/STOP switch on
FX
2C
and FX
2N(C)
units to the STOP position.
•FX
2N(C)
units do not have a RUN terminal. One of the inputs X0 to X17 (X0 to X7 for FX
2N
-
16M) on the MPU should be confi
g
ured as a RUN terminal in the parameter settin
g
s.
M8000
M8035
X1
M8036
M8037
24V S/S0V RUN X0 X1
RUN
STOP
FX base unit configured as source
input (example only)
Forced STOP
command
Forced RUN
command
Forced RUN mode