Registers; Data Registers - Mitsubishi MELSEC System Q Manual

Devices in Detail
5.5

Registers

The PLC's relays are used to store the results of operations temporarily. However, relays can
only store values of On/Off or 1/0, which means that they are not suitable for storing measure-
ments or the results of calculations. Values like this can be stored in the "registers" of the con-
trollers of the MELSEC System Q.
Registers are 16 bits or one word wide (see section 4.2). You can create "double word" regis-
ters capable of storing 32-bit values by combining two consecutive data registers.
Register:
Double word register:
A normal register can store values from 0000
isters can store values from 00000000
The controllers of the MELSEC System Q have a large number of instructions for using and
manipulating registers. You can write and read values to and from registers, copy the contents
of registers, compare them and perform math functions on their contents (see chapter 6).
5.5.1

Data registers

Data registers can be used as memory in your PLC programs. A value that the program writes
to a data register remains stored there until the program overwrites it with another value.
When you use instructions for manipulating 32-bit data you only need to specify the address of
a 16-bit register. The more significant part of the 32-bit data is automatically written to the next
consecutive register. For example, if you specify register D0 to store a 32-bit value D0 will con-
tain bits 0 through 15 and D1 will contain bits 16 through 31.
MELSEC System Q Beginners Manual
1 sign bit
16 bit
14 13
2 2
0: = positive value
1: = negative value
1 sign bit
32 bit
30 29
2 2
0: = positive value
1: = negative value
15 data bits
12 11 10 9 8 7 6
2 2 2 2 2 2 2
31 data bits
. . .
28
2
to FFFF (-32,768 to 32,767). Double-word reg-
H H
to FFFFFFFF (-2,147,483,648 to 2,147,483,647).
H H
5 4 3 2 1 0
2 2 2 2 2 2
. . .
2 1 0
2 2 2
Registers
5 – 11