Chapter 16 PLC Function ApplicationsMS300 (High Speed Model)
16-26
Relationship between bits, digits, nibbles, words, and double words in a binary system
(see figure below):
NB0NB1NB2NB3NB4NB5NB6NB7
BY3 BY2 BY1 BY0
W1
DW
W0
Double Word
Word
Byte
Nibble
Bit
Octal Number, OCT
The external input and output terminals of a DVP-PLC are numbered using octal numbers
Example: External input: X0~X7，X10~X17…(Device number table);
External output: Y0~Y7，Y10~Y17…(Device number table)
Decimal Number, DEC
Decimal numbers are used for the following purposes in a PLC system:
The setting values of timer T or counter C, such as TMR C0 K50. (K constant)
The numbers of devices including M, T, C, or D, such as M10 or T30. (device number)
Used as a operand in an application command, such as MOV K123 D0. (K constant)
Binary Code Decimal, BCD
Uses one nibble or 4 bits to express the data in a decimal number; a series of 16 bits can therefore
express a decimal number with 4 nibbles. Chiefly used to read the input value of a fingerwheel
numerical switch input or output a numerical value to a seven-segment display drive.
Hexadecimal Number, HEX
Applications of hexadecimal numbers in a PLC system: Used as operands in application commands,
such as MOV H1A2B D0. (H constant)
Constant K
Decimal numbers are usually prefixed with a "K" in a PLC system, such as K100. This indicates that it
is a decimal number with a numerical value of 100.
Exceptions: K can be combined with bit device X, Y, M, or S to produce data in the form of a nibble,
byte, word, or double word, such as in the case of K2Y10 or K4M100. Here K1
represents a 4-bit combination, and K2-K4 variously represent 8-, 12-, and 16-bit
combinations.
Constant H
Hexadecimal numbers are usually prefixed with the letter "H" in a PLC system, such as in the case of
H100, which indicates a hexadecimal number with a numerical value of 100.
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