Chapter 16 PLC Function ApplicationsMS300
685
16-5-1 Introduction to device functions
Input/output contact functions
Input contact X has this function: input contact X is connected with an input device, and reads input
signals entering the PLC. There are no restrictions on the number of times that the input contact A or
B appear in the program. The ON/OFF state of input contact X changes as the input device switches
between ON and OFF; you cannot use a peripheral device (WPLSoft) to force contact X ON or OFF.
Output contact Y functions
The output contact Y sends an ON/OFF signal to drive the load connected to output contact Y. There
are two types of output contacts: relays and transistors. There are no restrictions on the number of
times that contact A or B of an output contact Y appear in a program, but it is recommended that you
use the number of output coil Y only once in a program; otherwise the output state when the PLC
performs program scanning is determined by the program's final output Y circuit.
Figure 16-50
Numerical value, constant [K] / [H]
K-2,147,483,648–K2,147,483,647
The PLC uses five types of numerical values to implement calculations based on its control tasks; the
following topics explain the use and function of the different numerical values.
Binary Number, BIN
The PLC's numerical operations and memory employ binary numbers. The following table explains
terms related to binary numbers.
Bits are the fundamental units of binary values, and have a state of either 1 or 0.
Comprised of a series of 4 bits (such as b3–b0); can be used to express a one-
nibble decimal number 0–9 or hexadecimal number: 0–F.
Comprised of a series of two nibbles (i.e. 8 bits, b7–b0); can express a
hexadecimal number: 00-FF.
Comprised of a series of two bytes (i.e. 16 bits, b15–b0); can express a
hexadecimal number with four nibbles: 0000–FFFF.
Comprised of a series of two words (i.e. 32 bits, b31–b0); can express a
hexadecimal number with eight nibbles: 00000000–FFFFFFFF
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