# Cos

Implement control signal based cosine function

Since R2020b

## Description

The Cos block computes the cosine of input signal. The block uses the coordinate rotation digital computer (CORDIC) approximation method. For more information, see CORDIC approximation method in Algorithms. The block has control signals that indicate whether the input and output data are valid. You can also specify the number of iterations of the algorithm and the latency strategy.

To use this block in your Simulink® model, open the `HDLMathLib` library by entering this command in the MATLAB® Command Window:

`open_system('HDLMathLib')`

### Latency Considerations

You can simulate the Cos block with latency. This block is a masked subsystem that contains a MATLAB Function block, `LumpLatency`. The subsystem uses this MATLAB Function block to compute the latency based on the Number of iterations. To view the function that computes the latency of the block, open the `LumpLatency` block in the masked subsystem. To view inside the mask, click the ⇩ icon on the block.

The maximum latency LMax of Cos block is given by this equation:

LMax = N + 1

where N is the value of the Number of iterations parameter.

The minimum latency LMin of Cos block is `2` when Number of iterations is less than or equal to `2`. For the number of iterations greater than `2`, the minimum latency is given by this equation:

LMin = 2 + `ceil`((N -1) / 3)

The block supports four latency modes. You can specify a custom latency value by setting the Latency Strategy parameter to `Custom`. For more information, see Custom latency.

## Limitations

• The block does not support floating-point data types, such as `half`, `single`, and `double`.

## Ports

### Input

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Input data signal to compute cosine function. The input value ranges from -2π to 2*π.

Data Types: `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `Boolean` | `fixed point` | `bus`

Input control signal that indicates whether the input signal is valid.

Data Types: `Boolean`

### Output

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Output data signal that is the cosine of the input signal.

Data Types: `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `Boolean` | `fixed point` | `bus`

Output control signal that indicates whether output signal is valid.

Data Types: `Boolean`

## Parameters

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Specify the number of iterations for CORDIC algorithm.

#### Programmatic Use

 Block Parameter: `iter` Type: character vector Values: ```Integer values``` Default: `'11'`

Specify whether to map the blocks in your design to minimum, maximum, custom, or zero latency. For more information, see LatencyStrategy.

#### Programmatic Use

 Block Parameter: `latencyMode` Type: character vector Values: `'Max'` | `'Min'` | `'Custom'` | `'Zero'` Default: `'Max'`

When you set Latency strategy to `Custom`, use this parameter to specify the custom latency value. The latency must be a nonnegative integer in the range [0, L], where L is the maximum latency value of Cos block. For more information, see CustomLatency.

#### Dependency

To enable this parameter, set Latency strategy to `Custom`.

#### Programmatic Use

 Block Parameter: `customLatencyValue` Type: Integer Values: ```0 to Max latency``` Default: `0`

## Tips

The block supports HDL code generation using HDL Coder™. HDL Coder provides additional configuration options that affect HDL implementation and synthesized logic. For more information, see HDL Block Properties.

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## References

[1] Volder, Jack E., “The CORDIC Trigonometric Computing Technique.” IRE Transactions on Electronic Computers EC-8 (1959); 330–334.

[2] Andraka, Ray “A Survey of CORDIC Algorithm for FPGA Based Computers.” Proceedings of the 1998 ACM/SIGDA Sixth International Symposium on Field Programmable Gate Arrays. Feb. 22–24 (1998): 191–200.

[3] Walther, J.S., “A Unified Algorithm for Elementary Functions,” Proceedings of the Spring Joint Computer Conference, May 18-20, 1971: 379–386.

[4] Schelin, Charles W., “Calculator Function Approximation,” The American Mathematical Monthly 90, no. 5 (1983): 317–325.

## Version History

Introduced in R2020b