I/O Assignment; Concept Of Assigning - Mitsubishi Electric FX Series Training Manual

The Hardware

I/O Assignment

2.11
The assignment of the inputs and outputs in a PLC of the MELSEC FX family is fixed and can not
be altered.
When power is turned on after input/output powered extension units/blocks have been con-
nected, the base unit automatically assigns the input/output numbers (X/Y) to the units/blocks.
Therefore, it is unnecessary to specify the input/output numbers with parameters.
Input/output numbers are not assigned to special function units/blocks.
2.11.1

Concept of assigning

Input/output numbers (X/Y) are octal
The inputs and outputs of a PLC of the MELSEC FX family are counted in the octal numeral sys-
tem. This is a base-8 number system and uses the digits 0 to 7.
The following table shows a comparison between some decimal and some octal numbers:
Octal numbers are assigned as input/output numbers (X/Y) as shown below.
– X000 to X007, X010 to X017, X020 to X027......, X070 to X077, X100 to X107...
– Y000 to Y007, Y010 to Y017, Y020 to Y027......, Y070 to Y077, Y100 to Y107...
Numbers for added input/output unit/block
To an added input/output powered extension unit/block, input numbers and output numbers fol-
lowing the input numbers and output numbers given to the preceding device are assigned.
The last digit of the assigned numbers must begin with 0.
For example, when the last number on the preceding device is Y43, the output numbers are
assigned to the next device starting from Y50.
Training Manual GX IEC Developer
Decimal
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
:
Octal
0
1
2
3
4
5
6
7
10
11
12
13
14
15
16
17
20
:
I/O Assignment
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