Setting And Resetting Devices - Mitsubishi Electric FX2N Beginners Manual

An Introduction to Programming
Evaluating a falling signal pulse
Ladder Diagram
M235
0
If X10 is off (0) and M235 is on (1) relay M374 is switched on for the
duration of a single program cycle.
With the exception of the pulse trigger characteristic the functions of the LDP, LDF, ANDP,
ANDF, ORP and ORF instructions are identical to those of the LD, AND and OR instructions.
This means that you can use pulse-trigger operations in your programs in exactly the same
way as the conventional versions.
3.4.8

Setting and resetting devices

Instruction
SET
RST
The SET instruction can be used to set outputs (Y), relays (M) and state relays (S).
The RST instruction can be used to reset outputs (Y), relays (M), state relays (S), timers (T), counters (C) and re-
gisters (D, V, Z).
The signal state of an OUT instruction will normally only remain "1" as long as the result of the
operation connected to the OUT instruction evaluates to "1". For example, if you connect a
pushbutton to an input and a lamp to the corresponding output and connect them with an LD
and an OUT instruction the lamp will only remain on while the button remains pressed.
The SET instruction can be used to use a brief switching pulse to switch an output or relay on
(set) and leave them on. The device will then remain on until you switch it off (reset) with a RST
instruction. This enables you to implement latched functions or switch drives on and off with
pushbuttons. (Outputs are generally also switched off when the PLC is stopped or the power
supply is turned off. However, some relays also retain their last signal state under these condi-
tions – for example a set relay would then remain set.)
To enter a SET or RST instruction in Ladder Diagram format just click on the icon shown in the
table above in GX Works2, or press the F8 key. Then enter the instruction and the name of the
device you want to set or reset, for example SET Y1 .
FX Beginners Manual
X010
M374
1
M235
0
ON (1)
X10
OFF (0)
1
M374
0
Function
Set a device ,
(assign signal state "1")
Reset a device ,
(assign signal state "0")
The Basic Instruction Set
Instruction List
0 LD M235
1 ANDF X010
2 OUT M374
t
Symbol GX Works2 FX
SET
RST
F8
F8
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