Siemens PLC programming: BCD, Integer, Double Integer, Real

Let’s study the working converters in Siemens PLC programming commands: BCD to Integer, Integer to BCD, Integer to Double Integer, BCD to Double Integer, Double Integer to Real.

Siemens PLC programming

Data types are used to identify the type of data used in the user program. Its a data storage format that can contain a specific type or range of values. When PLC program stores data in variables must be assigned to specific data type like Bool (1 Bit), integer (16 bit), Word (16 bit), Double Integer (32 bit) and Real (32 bit).

While processing inputs and outputs in PLC program, conversion like BCD to an integer, Integer to a double integer, etc are much needed.

BCD to Integer Instruction

BCD to Integer instruction is used to convert BCD coded number to integer format. Input data can be read at IN. Input condition can give EN input and ENO is output, it has the same signal as EN. The least significant bit in BCD format is the sign bit.

Example 1:

Input IN : 0000 0001 0001 1000

Output OUT : 118

Example 2:

Input IN :1000 0001 0001 1000

Output OUT : -118

Integer to BCD Instruction

Integer to BCD instruction is used to convert integer format to BCD coded numbers. Input data can be read at IN. Input condition can give EN input and ENO is output, it has the same signal as EN.

Example 1:

Input (IN) : 118

Output (OUT) : 0000 0001 0001 1000

Example 2:

Input (IN):  -118

Output (OUT): 1000 0001 0001 1000

Integer to Double Integer Instruction

Integer to Double Integer instruction is used to convert the data which is in 16 bit to 32 bit. Input data can be read at IN. Input condition can give EN input and ENO is output, it has the same signal as EN.

Example 1:

Input (IN) : 90

Output (OUT) : L # 90     (Decimal Format )

Example 2:

Input (IN):  0000 0000 0101 1010

Output (OUT): 0000 0000 0000 0000 0000 0000 0101 1010    (Binary format)

BCD to Double Integer Instruction

BCD to Double Integer instruction is used to convert BCD coded numbers to double integer format(32 bit ). Input data can be read at IN. Input condition can give EN input and ENO is output, it has the same signal as EN. The least significant bit in BCD format is the sign bit.

Example 1:

Input IN : 0000 0010 0101 0101

Output OUT : 255

Example 2:

Input IN :1000 0100 0100 0010 1000 0010 0101 0101

Output OUT : -4428255

Double Integer to BCD Instruction

Double Integer to BCD instruction is used to convert a double integer format(32 bit ) to BCD coded number. Input data can be read at IN. Input condition can give EN input and ENO is output, it has the same signal as EN. The least significant bit in BCD format is the sign bit.

Example 1:

Input IN : 225

Output OUT : 0000 0010 0101 0101

Example 2:

Input IN : -4428255

Output OUT : 1000 0100 0100 0010 1000 0010 0101 0101

Double Integer to Real Instruction

Double Integer to Real instruction is used to convert a double integer format(32 bit ) to a floating-point number (32bit). Input data can be read at IN. Input condition can give EN input and ENO is output, it has the same signal as EN. The least significant bit in BCD format is the sign bit.

Example 1:

Input IN : 987

Output OUT: 987.0

Example 2:

Input IN: 209834

Output OUT: 209834.0

Ladder Logic

Ladder Description

Network 1:

Input I0.0 is pressed, BCD to I instruction reads the value in MW0 and convert that to a corresponding integer value and result in the output to MW2. Q0.0 enables as long as I0.0 enables.

Network 2:

Input I0.0 is pressed; I to BCD instruction read the value in MW4 and convert that to corresponding BCD value and result in the output to MW6. Q0.1 enables as long as I0.0 enables.

Network 3:

Input I0.0 has pressed I to DI instruction reads the value in MW8 and convert that to a corresponding integer value and result in the output to MD10. Q0.2 enables as long as I0.0 enables.

Network 4:

Input I0.0 is pressed; BCD to DI instruction reads the value in MD14 and convert that to corresponding double integer value and result in the output to MD18. Q0.3 enables as long as I0.0 enables.

Network 5 :

Input I0.0 is pressed, DI to BCD instruction reads the value in MD22 and convert that to corresponding BCD  value and result in the output to MD26. Q0.4 enables as long as I0.0 enables.

Network 6:

Input I0.0 is pressed; DI to R instruction reads the value in MD30 and convert that to corresponding floating-point value and result in the output to MD34. Q0.5 enables as long as I0.0 enables.

Variable Table:

Variable is used to view the inputs and outputs in different formats.

In Siemens, MW is the address used for integer data, MD is the address used for double integer data.

Status Value in Variable table is used to see the input and output values.

Modify the value in the variable table is used to give input data.

Author: Hema Sundaresan

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