Memory bits used to control inputs and output signals in PLC /Addressing in PLC/PLC Automation by Bestway

Memory bits used to control inputs and output signals in PLC

In Micro controller based device memory is divided into three category i.e. Program, Discrete or Digital Registers and word. Data is held in these Registers. These  Registers come in different sizes, and hold different kinds of data.

Bits or Boolean: Can have values 1 or 0 Condition.  1 is represents On while 0 represents Off.  Bits are the building block for all other types of data. These Boolean values are used for all the input and output devices like sensor and switch inputs, as well as motor or other outputs.

Integers(Multiple Bits):  Multiple-bit integers are usually  8, 16, or 32 consecutive bits and can hold only whole number values. Whole numbers  also Called as Characters (char), Integers (int), long Integers (long int) or Words. Depends on  bit size and whether they are signed or unsigned.   Unsigned  Integers are positive numbers, while signed are positive or negative.
Floating point (Decimal) numbers: Numbers with decimal points, and can be positive or negative integers. They are called floating point numbers (Float), with their larger variety called double floats.

I.              BOOL: Digital Data (True / False)

II.            BYTE: Numerical Data / Bitwise Data (0 - 255)

III.           INT: Numerical Data (-32768 - 32767)

IV.          UINT: Numerical Data (0 - 65535)

V.           SINT: Numerical Data (-128 - 127)

VI.          USINT: Numerical Data (0 - 255)

VII.         DINT: Numerical Data (-2147483648 - 2147483647)

VIII.       WORD: Numerical Data / Bitwise Data (0 - 65535)

IX.          DWORD: Numerical Data / Bitwise Data (0 - 4294967295)

X.           REAL: Numerical Data (-3.402823e+38 - 3.402823e+38)

XI.          ARRAY: Array of Any Data type (Declared as "ARRAY [0..10]      OF DataType)

Understanding the PLC input output Data Types.

Instruction: ADD: Adds the input operands and places the sum in the output register

Inputs

Signal	Data type	Description
EN	BOOL	Enables block operation
IN1 & IN2	SINT,INT,DINT,USINT,UINT,UDINT,REAL,LREAL,TIME,TOD	Input values to be added

Outputs

Signal	Data type	Description
ENO	BOOL	Indicates completion of operation
O	BOOL	Overflow signal, HIGH when the result exceeds the defined variable range
OUT	SINT,INT,DINT,USINT,UINT,UDINT,REAL,LREAL,TIME,TOD	Output value after addition of 2 input values

Representation in Ladder Logic:

Variable View:

When you are activating the load using PLC, must check the data type for particular devices or blocks used in the programming, most of the plc coming with inbuilt address only you need to give inputs address according to the types of plc.

Example.

To describe input and output address. I taken On delay Timer which from the Siemens PLC ladder logic.

On delay Timer

In on delay timer, when input is on output is on after some time delay.

Where,

            In denotes Input,

            Q denotes output,

            PT denotes Preset Time,

            ET denotes Enable Time.