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● Usually, 8 bits are called 1 byte, and 16 bits (2 bytes) are called 1 word.
0 000 0000 1001 1101
1 byte
1 word (2 byte)
1001 1101
1 bit
● Registers of each word device in the MELSEC-Q series programmable controller consist of 16
bits.
• Data register D
• Current value of
timer T
• Current value of
counter C
• File register R
• Link register W
32768
16384
8192
4096
2048
1024
512
256
128
64
32
16
8
4
2
D0
1
(Binary bit weight)
● The following two ranges of numbers can be processed in 16 bits (1 word).
1) 0 to 65535
2) -32768 to +32767
● The range 2) is available for the MELSEC-Q programmable controller.
The negative numbers adopt two's complement against the positive numbers (1 to +32767).
● In the two's complement
, each binary bit is inverted, and 1 is added to the least significant bit.
Example)
How to calculate the two's complement against 1
0 000 0000 0000 0001
1 1 1 110
Add 1 to the least
significant bit.
Invert all bits.
The most significant bit of "1" means negative.
The most si
g
nificant bit corres
p
onds to the si
g
n of a si
g
ned binar
y
number.
1111111111
0
000 0000 0000 0001
1 1 1 1111111111111
1
-1
Numerical values used by MELSEC-Q series programmable controller