Square Root (SQRT)
This table lists the controllers and applications that support this instruction.
Architecture | Standard applications | Safety applications |
|---|---|---|
CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Yes | No |
CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Yes | Yes |
The Square Root (SQRT) instruction and operator computes the square root of the Source and places the result in Dest.
TIP:
In Logix Designer version 36, the mnemonic for this instruction changed from SQR to SQRT.
Available Languages
Ladder Diagram
Function Block Diagram
Function Block Diagram supports these elements:
FBD Block
FBD Function
TIP:
FBD Function is applicable to CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers only.
Structured Text
This instruction is not available in structured text.
TIP:
Use SQRT as an operator in an expression to compute the same result. Refer to Structured Text Syntax for more information on the syntax of expressions and assignments within structured text.
Operands
IMPORTANT:
Unexpected operation may occur if:
- Output tag operands are overwritten.
- Members of a structure operand are overwritten.
- Except when specified, structure operands are shared by multiple instructions.
There are data conversion rules for mixing numeric data types within an instruction. See Data Conversions.
Ladder Diagram
Operand | Data Type CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Format | Description |
|---|---|---|---|---|
Source | SINT INT DINT REAL | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | immediate tag | Computes the square root of this value. |
Dest | SINT INT DINT REAL | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | tag | Tag to store the result of the instruction. |
Function Block Diagram
FBD Block
Operand | Data Type | Format | Description |
|---|---|---|---|
SQRT | FBD_MATH_ADVANCED | tag | SQRT structure |
FBD_MATH_ADVANCED Structure
Input Members | Data Type | Description |
|---|---|---|
EnableIn | BOOL | Enable input. If false, the instruction does not execute and outputs are not updated.
Default is true. |
Source | REAL | Find the square root of this value. |
Output Members | Data Type | Description |
|---|---|---|
EnableOut | BOOL | Indicates if the instruction executed without fault when it was enabled. |
Dest | REAL | Result of the instruction. |
FBD Function
TIP:
FBD Function is applicable to CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers only.
Input Operand (Left Pin) | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Description |
|---|---|---|
SourceA | SINT USINT INT UINT DINT UDINT LINT ULINT REAL LREAL | Computes the square root of this value. |
Output Operand (Right Pin) | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Description |
|---|---|---|
Dest | DINT UDINT LINT ULINT REAL LREAL | Result of the function. |
See FBD Functions.
Description
If the Dest is not an LREAL/REAL, the instruction handles the fractional portion of the result as follows:
If the Source is: | (For CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers) The fractional portion of the result: | Example | (For CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers) The fractional portion of the result: | Example | ||||
|---|---|---|---|---|---|---|---|---|
any elementary integer tag/value | Truncates | Source | DINT | 3 | Rounds | Source | DINT | 3 |
Dest | DINT | 1 | Dest | DINT | 2 | |||
any floating point tag/value | Rounds | Source | REAL | 3.0 | Rounds | Source | REAL | 3.0 |
Dest | DINT | 2 | Dest | DINT | 2 | |||
If the Source is negative, the instruction takes the absolute value of the Source before calculating the square root.
For the
CompactLogix
5370, ControlLogix
5570, Compact GuardLogix
5370, and GuardLogix
5570 controllers, if the Source is an integer data type and the Dest is an integer data type, the instruction truncates the result. For example, if the integer Source value is 3, the result is 1.732, and the Dest value becomes 1.If the Source is a real data type and the Dest is an integer type, the instruction rounds the result. For example, if the real Source value is 3.0, the result is 1.732, and the Dest value becomes 2.
Affects Math Status Flags
Controllers | Affects Math Status Flags |
|---|---|
CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Conditional |
CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Yes |
See Math Status Flags.
Major/Minor Faults
None specific to this instruction. See Index Through Arrays for array-indexing faults.
Execution
Ladder Diagram
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
Rung-condition-in is false | Set Rung-condition-out to Rung-condition-in. |
Rung-condition-in is true | Set Rung-condition-out to Rung-condition-in. Dest = square root of Source. |
Postscan | N/A |
Function Block Diagram
FBD Block
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
EnableIn is false | Set EnableOut to EnableIn. |
EnableIn is true | Dest. = square root of Source. If overflow occurs Clear EnableOut to false else Set EnableOut to true |
Instruction first run | N/A |
Instruction first scan | N/A |
Postscan | N/A |
FBD Function
TIP:
FBD Function is applicable to CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers only.
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
Normal Scan | Dest = square root of Source |
Instruction first run | N/A |
Instruction first scan | N/A |
Postscan | N/A |
Examples
Ladder Diagram
Function Block Diagram
FBD Block
FBD Function
Structured Text
REAL_dest := SQRT(INT_src);
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