Two-Argument Arctangent (ATAN2)
This information applies to the Compact GuardLogix 5380, CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, and GuardLogix 5580 controllers.
The ATAN2 instruction takes the two-argument arc tangent of the Source values and stores the result in the Destination (in radians). The ATAN2 operator/function computes the arc tangent of the Source and returns the FLOAT result. The resulting value in the Destination is greater than or equal to -
p
and less than or equal to p
(where p
= 3.141593).Available Languages
Ladder Diagram
Function Block Diagram
Function Block Diagram supports only the FBD function:
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 ATAN2 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 structured operand are overwritten.
- Except when specified, structure operands are shared by multiple instructions.
Ladder Diagram
Operand | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Format | Description |
Source Y | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | immediate tag | Source Y of ATAN2 Input |
Source X | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | immediate tag | Source X of ATAN2 Input |
Dest | REAL LREAL | tag | Tag to store result of the instruction. |
Function Block Diagram
FBD Function
Operand | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Description |
Source Y | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | Source Y of ATAN2 Input |
Source Y | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | Source X of ATAN2 Input |
Output Operand (Right Pin) | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Description |
Dest | REAL LREAL | Result of the function. |
See FBD Functions.
Operator Aspects
The ATAN2 operator can be used in various RLL expressions. Similarly, the ATAN2 function is invoked in Structured Text statements. ATAN2 returns a FLOAT result containing the result of two argument arc tangent of the Source Y and Source X. Depending on the context, this value can then be type converted if appropriate.
Affects Math Status Flags
Controllers | Affects Math Status Flag |
CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Conditional, 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 = ATAN2(Source Y, Source X) |
Postscan | N/A |
Function Block Diagram
FBD Function
Condition/State | Action Taken |
Prescan | N/A |
Normal Scan | Dest = ATAN2(Source Y, Source X) |
Instruction first run | N/A |
Instruction first scan | N/A |
Postscan | N/A |
Examples
Ladder Diagram
Function Block Diagram
FBD Function
Structured Text
REAL_dest := ATAN2(REAL_srcY, REAL_srcX);
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