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Chapter 6 Compute/Math Instructions (CPT, ADD, SUB, MUL, DIV, MOD, SQR, SQRT, NEG, ABS)
Square Root (SQR)
Operands:
The SQR instruction computes the square root of the Source and places the result in the Destination.
dest := SQRT(source);
Relay Ladder
Operand
Source
Type
SINT
INT
DINT
Format
immediate tag
Description
find the square root of this value
REAL
A SINT or INT tag converts to a DINT value by sign-extension.
Destination SINT tag tag to store the result
INT
DINT
REAL
Structured Text
Use SQRT as a function. This expression computes the square root of source and stores the result in dest.
See Appendix C, Structured Text Programming for information on the syntax of expressions within structured text.
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Compute/Math Instructions (CPT, ADD, SUB, MUL, DIV, MOD, SQR, SQRT, NEG, ABS) Chapter 7
Function Block
Operand
SQR tag
Type
FBD_MATH_ADVANCED
FBD_MATH_ADVANCED Structure
Format
structure
Description
SQR structure
Input Parameter
EnableIn
Source
Data Type
BOOL
REAL
Output Parameter
EnableOut
Dest
Data Type
BOOL
REAL
Description
Enable input. If cleared, the instruction does not execute and outputs are not updated.
Default is set.
Find the square root of this value.
Valid = any float
Description
The instruction produced a valid result.
Result of the math instruction. Arithmetic status flags are set for this output.
Description:
If the Destination is not a REAL, the instruction handles the fractional portion of the result as follows:
If The Source Is
not a REAL a REAL
Then The Fractional
Portion Of The Result
truncates
Example
rounds
Source
Destination
Source
Destination
DINT
DINT
REAL
DINT
3
1
3.0
2
If the Source is negative, the instruction takes the absolute value of the Source before calculating the square root.
Arithmetic Status Flags:
Arithmetic status flags are affected.
Fault Conditions:
none
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Chapter 6 Compute/Math Instructions (CPT, ADD, SUB, MUL, DIV, MOD, SQR, SQRT, NEG, ABS)
Condition
prescan rung-condition-in is false rung-condition-in is true postscan
Condition
prescan instruction first scan instruction first run
EnableIn is cleared
EnableIn is set postscan
Execution:
Relay Ladder
Action
The rung-condition-out is set to false.
The rung-condition-out is set to false.
Destination
=
Source
The rung-condition-out is set to true.
The rung-condition-out is set to false.
Function Block
Action
No action taken.
No action taken.
No action taken.
EnableOut is cleared.
The instruction executes.
EnableOut is set.
No action taken.
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Compute/Math Instructions (CPT, ADD, SUB, MUL, DIV, MOD, SQR, SQRT, NEG, ABS) Chapter 7
Example:
Calculate the square root of value_1 and place the result in sqr_result.
Relay Ladder
Structured Text
sqr_result := SQRT(value_1);
Function Block
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