Introduction Of Devices Constructing Plc; Relationship Among Devices - Mitsubishi FX3U Series Programming Manual

FX /FX Series Programmable Controllers
3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2.5

Introduction of Devices Constructing PLC

Many relays, timers, and counters are built into an FX
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.
2.5.1

Relationship among devices

Arrows show transfer of signals.
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".
Output terminal
or output
connector
30
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 scale.
Timer: T
There are many
timers inside the
PLC.
The assigned
device mnemonic
is "T".
Contact for external output from output relay
(one NO contact)
The PLC has built-in output contacts in accordance with its
scale.
2.5 Introduction of Devices Constructing PLC
/FX PLC, with many NO (normally open) contacts
3U 3UC
Input terminal or
input connector
1 2 3 4
Counter: C
There are many
counters inside the
PLC.
The assigned
device mnemonic
is "C".
2 Overview (Sequence Program)
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".