Chapter 16 PLC Function ApplicationsMS300
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The following diagram shows the relationship between bits, digits, nibbles, words, and double words
in a binary system (see figure below).
Figure 16-51
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
A PLC uses decimal numbers for the following purposes:
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).
An operand in an application command, such as MOV K123 D0 (K constant).
Binary Coded Decimal, BCD
Uses one nibble or four bits to express the data in a decimal number; a series of 16 bits can therefore
express a decimal number with four nibbles. These are used to read the input value of a rotating
numerical switch to input or output a numerical value to a seven-segment display drive.
Hexadecimal Number, HEX
A PLC uses hexadecimal numbers as operands in application commands, such as MOV H1A2B D0 (H
constant).
Constant K
PLC’s usually prefixed decimal numbers with K, such as K100. This indicates that it is a decimal
number with a numeric value of 100.
Exceptions: You can combine K with a 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 represent 8-, 12-, and 16-bit combinations.
Constant H
PLC’s usually prefixed hexadecimal numbers with H, such as in the case of H100. This indicates a
hexadecimal number with a numeric value of 100.
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