Mitsubishi Electronics FX3G User Manual

FX

3S

/FX

3G

/FX

3GC

/FX

3U

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3UC

 Series

Programming Manual - Basic & Applied Instruction Edition

6 What to Understand before Programming

When a coil gives double outputs (double coils) in a sequence program, the priority is given to the latter one.

Suppose that the same coil Y003 is used in two positions as shown in
the figure on the right.
For example, suppose the X001 is ON and X002 is OFF.

In the first coil Y003, the image memory turns ON and the output
Y004 turns ON also because the input X001 is ON.
In the second coil Y003, however, the image memory is set to OFF
because the input X002 is OFF.
Accordingly, the actual output to the outside is "Y003 = OFF, Y004 =
ON".

Double outputs (double coils) do not cause illegal input (program error), but the operation is disrupted as described
above.
Change the program as shown in the example below.

SET, RST or jump instruction can be used instead, or the same output coil can be programmed at each state by step
ladder instructions.
When step ladder instructions are used, if an output coil located in the main routine is also used in a state, it is handled
as a double coil. It is better to avoid such programming.

X001

  Input processing

  X001 = ON   X002 = OFF

Y003

First

Y003

Y004

X002

Y003

Second

  Output processing

  Y003 = OFF   Y004 = ON

A

B

Y000

Ignored

C

Y000

E

D

A

B

Y000

C

E

D

A

B

M100

C

E

D

M101

M100

M101

Y000

or

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