Inputs and Outputs
4.1 Inputs and Outputs
The PLC’s inputs and outputs connect it to the process that it is controlling. When an input is polled by the PLC program the voltage on the input terminal of the controller is measured. Since these inputs are digital they can only have two signal states, ON or OFF. When the volt- age at the input terminal reaches 24V the input is on (state “1”). If the voltage is lower than 24V the input evaluates as off (signal state “0”).
In MELSEC PLCs the identifier “X” is used for inputs. The same input can be polled as often as necessary in the same program.
NOTE
The PLC cannot change the state of inputs. For example, it is not possible to execute an OUT instruction on an input device.
If an output instruction is executed on an output the result of the current operation (the signal state) is applied to the output terminal of the PLC. If it is a relay output the relay closes (all relays have make contacts). If it is a transistor output the transistor makes the connection and acti- vates the connected circuit.
The illustration on the left shows an example of how you can connect switches to the inputs and lamps and contactors to the out- puts of a MELSEC PLC.
X000 X001 X002
Y000 Y001 Y002
The identifier for output devices is “Y”. Outputs can be used in logic operation instructions as well as with output instructions. However, it is important to remember that you can never use an output instruction on the same output more than once (see also chapter 3.4.2).
FX Beginners Manual 4–1
Inputs and Outputs Devices in Detail
The following table provides a general overview of the inputs and outputs of the controllers of the MELSEC FX family.
Device identifier
Device type
Bit device
Possible values
0 or 1
Device address format
Octal
6 (X00–X05)
4 (Y00–Y03)
8 (X00–X07)
6 (Y00–Y05)
FX 1S
12 (X00–X07, X10, X11, X12, X13)
8 (Y00–Y07)
16 (X00–X07, X10–X17)
14 (Y00–Y07, Y10–Y15)
8 (X00–X07)
6 (Y00–Y05)
14 (X00–X07, X10–X15)
10 (Y00–Y07, Y10, Y11)
24 (X00–X07, X10–X17, X20–X27)
16 (Y00–Y07, Y10–Y17)
36 (X00–X07, X10–X17, X20–X27,
FX 1N
X30–X37, X40, X41, X42, X43)
24 (Y00–Y07, Y10–Y17, Y20–Y27)
The total number of inputs can be
The total number of outputs can be increased to max. 84 (X123) with expan- increased to max. 64 (Y77) with expan- sion modules. However, the sum of all
sion modules. However, the sum of all
inputs and outputs cannot exceed 128.
inputs and outputs cannot exceed 128.
8 (X00–X07)
8 (Y00–Y07)
16 (X00–X07, X10–X17)
16 (Y00–Y07, Y10–Y17)
24 (Y00–Y07, Y10–Y17, Y20–Y27) Number of devi-
24 (X00–X07, X10–X17, X20–X27)
ces and addres-
32 (Y00–Y07, Y10–Y17, Y20–Y27, ses (depends on
32 (X00–X07, X10–X17, X20–X27,
FX 2N
X30–X37)
Y30–Y37)
controller base
40 (Y00–Y07, Y10–Y17, Y20–Y27, unit type)
40 (X00–X07, X10–X17, X20–X27,
X30–X37, X40–X47)
Y30–Y37, Y40–Y47)
64 (X00–X07, X10–X17, X20–X27,
64 (Y00–Y07, Y10–Y17, Y20–Y27,
X30–X37, X40–X47, X50–X57,
Y30–Y37, Y40–Y47, Y50–Y57,
X60–X67, X70–X77)
Y60–Y67, Y70–Y77)
8 (X00–X07)
8 (Y00–Y07)
16 (X00–X07, X10–X17)
16 (Y00–Y07, Y10–Y17)
FX 2NC
32 (X00–X07, X10–X17, X20–X27,
32 (Y00–Y07, Y10–Y17, Y20–Y27,
X30–X37)
Y30–Y37)
48 (X00–X07, X10–X17, X20–X27,
48 (Y00–Y07, Y10–Y17, Y20–Y27,
X30–X37, X40–X47, X50–X57)
Y30–Y37, Y40–Y47, X50–X57)
8 (X00–X07)
8 (Y00–Y07)
16 (X00–X07, X10–X17)
16 (Y00–Y07, Y10–Y17)
24 (X00–X07, X10–X17, X20–X27)
24 (Y00–Y07, Y10–Y17, Y20–Y27)
FX 3U
32 (X00–X07, X10–X17, X20–X27,
32 (Y00–Y07, Y10–Y17, Y20–Y27,
X30–X37)
Y30–Y37)
40 (X00–X07, X10–X17, X20–X27,
40 (Y00–Y07, Y10–Y17, Y20–Y27,
X30–X37, X40–X47)
Y30–Y37, Y40–Y47)
* The total number of inputs can be increased to max. 248 (X367) with expansion modules. However, the sum of all
inputs and outputs cannot exceed 256.
MITSUBISHI ELECTRIC
Devices in Detail Relays