Arc Cosine (ACOS)
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 |
When enabled, the ACOS instruction takes the arc cosine of the Source value and stores the result in the Destination (in radians).
TIP:
In Logix Designer version 36, the mnemonic for this instruction changed from ACS to ACOS.
Available Languages
These are the available languages for Arc Cosine (ACOS).
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 ACOS 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 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 | Value to convert to arc cosine. |
Destination | SINT INT DINT REAL | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | tag | Tag to store result of the instruction. |
Function Block Diagram
FBD Block
Operand | Type | Format | Description |
ACOS | FBD_MATH_ADVANCED | tag | ACS structure |
FBD_MATH_ADVANCED Structure
Input Member | Data Type | Description |
EnableIn | BOOL | Enable input. If false, the instruction does not execute and outputs are not updated. Default is true. |
Source | REAL | Input to the trigonometric instruction. |
Output Member | 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.
Operand | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Description |
Source | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | Value to convert to arc cosine. |
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 ACOS operator can be used in various RLL expressions. Similarly, the ACOS function is invoked in Structured Text statements. ACOS returns a floating point result containing the arc cosine of the Source. Depending on the context this value may then be type converted if appropriate.
Description
The ACOS instruction takes the arc cosine of the Source value and stores the result in the Destination (in radians). The ACOS operator/function computes the arc cosine of the Source and returns the floating point result. The Source must be greater than or equal to -1 and less than or equal to 1. The resulting value in the Destination is greater than or equal to 0 or less than or equal to pi (where pi = 3.141593). If Source is smaller than -1 or greater than 1 then Destination is set to NAN.
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. |
CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Yes |
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 = arc cosine value of the 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 = arc cosine value of the Source. If overflow occurs Clear EnableOut to false. else Set EnableOut to true. |
Instruction first scan | N/A |
Instruction first run | N/A |
Postscan | N/A |
FBD Function
Condition/State | Action Taken |
Prescan | N/A |
Normal Scan | Dest = arc cosine value of the Source. |
Instruction first run | N/A |
Instruction first scan | N/A |
Postscan | N/A |
Example
Ladder Diagram
Function Block Diagram
FBD Block
FBD Function
Structured Text
REAL_dest := ACOS(REAL_src);
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