Mitsubishi Electronics FX3G User Manual

FX

3S

/FX

3G

/FX

3GC

/FX

3U

/FX

3UC

 Series

Programming Manual - Basic & Applied Instruction Edition

2 Overview (Sequence Program)

Many relays, timers, and counters are built into an FX

3S

/FX

3G

/FX

3GC

/FX

3U

/FX

3UC

 PLCs, with many NO (normally

open) contacts and NC (normally closed) contacts.
These contacts and coils are connected to make a sequence circuit.
A PLC is also equipped with data registers (D) and extension data registers (R) functioning as memory devices to
store numeric data values.

Arrows show transfer of signals.

4

1 2 3

Input terminal or
input connector

Input relay: X
Input relays function as receiving ports when the PLC receives signals from external
input switches.
The assigned device mnemonic is "X".
The PLC has built-in input relays in accordance with its size.

Auxiliary relay: M
There are many
auxiliary relays
inside the PLC.
The assigned
device mnemonic
is "M".

State relay: S
There are many
state relays inside
the PLC.
The assigned
device mnemonic
is "S".

Timer: T
There are many
timers inside the
PLC.
The assigned
device mnemonic
is "T".

Counter: C
There are many
counters inside the
PLC.
The assigned
device mnemonic
is "C".

Output relay: Y
Output relays
function as ports
when the PLC
drives external
loads.
There are many
output relays inside
the PLC.
The assigned
device mnemonic
is "Y".

Output terminal
or output
connector

Contact for external output from output relay
(one normally open contact)
The PLC has built-in output contacts in accordance with its
size.