Documentation

Frequency Output

Write to one or multiple frequency or PWM output channels

Description

Generate and output a pulse-width-modulated square wave to an analog output.

The square wave alternates between low (0) and high (1) with a specified frequency and duty cycle.

You specify the frequency in hertz (Hz).

You specify the duty cycle as a decimal fraction from 0 through 1 inclusive. The duty cycle determines the amount of time that the output signal value is high (1).

After you have added a Frequency Output block to your model, double-click the Frequency Output block to open the Block Parameters: Frequency Output dialog box.

Ports

Input

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Frequency setting of waveform generator. The data type and range of the input values depend upon the capabilities of the board.

Dependency

When you set Output signal frequency source to external, this port is visible.

Data Types: single | double | int8 | uint8 | int16 | uint16 | int32 | uint32

Duty cycle setting of waveform generator. The data type and range of the input values depend upon the capabilities of the board.

Dependency

When you set Output signal duty source to external, this port is visible.

Data Types: single | double | int8 | uint8 | int16 | uint16 | int32 | uint32

Output

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In normal or accelerator modes, returns the number of timer ticks that your model lags behind the real-time kernel. When the model lags by more than Maximum missed ticks, the software reports an error and simulation stops.

Dependency

When you select Show “Missed Ticks” port, this port is visible.

Data Types: double

Parameters

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When you click Install new board, the software displays a list of manufacturers of supported boards. When you select a manufacturer, the software displays a list of boards available from that manufacturer. When you select a board, the software adds the board to the list of registered boards and makes that board the current board.

By default, the initial selection in the list of registered boards is < no board selected >.

Dependency

When you select a board in the list of registered boards, the Delete current board and Board setup buttons are available.

To delete the current board, click this button. The initial selection of the list of registered boards changes to < no board selected >.

Dependency

To activate this parameter, select a board in the list of registered boards.

When you delete the current board, the Delete current board and Board setup buttons are no longer available.

To set up the board, click this button.

A board-specific dialog box opens to set up the board. For more information, see the board manufacturer documentation.

Dependency

To activate this parameter, select a board in the list of registered boards.

To deactivate this parameter, click Delete current board.

Enter a value, in seconds, that represents how frequently you want the block to execute and interact with the I/O hardware. The block synchronizes your model with the real-time clock at this sample rate.

If you are using a fixed-step solver, enter the value that you entered as the Fixed step size configuration parameter or an integer multiple of that value.

In normal or accelerator modes, enter the number of timer ticks that your model can lag behind the real-time kernel. When the model lags behind by this number or fewer timer ticks, the software assumes that the lag is temporary. It allows the model to catch up, even if the model misses some ticks. When the model lags by more than this number, the software reports an error and simulation stops.

In external mode, the software ignores this value.

In normal or accelerator modes, select this check box to send the number of missed ticks to output port Missed Ticks.

In external mode, the Missed Ticks port is zero.

In normal or accelerator modes, select this check box to grant other programs more CPU time while the kernel waits for a response from the hardware.

In external mode, the software ignores this value.

Enter a channel vector that selects the frequency output channels you are using on this board. The vector can be any valid MATLAB® vector form. For example, to select the first eight digital output channels, enter:

[1,2,3,4,5,6,7,8]

or

[1:8]

Select the source that specifies the frequency to output, in Hz. The Output signal frequency source can be either of the following:

  • internal — A tunable parameter named Frequency specifies the frequency.

  • external (default) — A signal specifies the frequency. Input port Frequency appears on the block to accept the signal.

    You can specify additional settings for Frequency initial value and Frequency final value.

Dependency

If you specify external (the default), port Frequency and the parameters Frequency initial value and Frequency final value are visible.

If you specify internal, Frequency replaces Frequency initial value and Frequency final value is disabled.

This parameter replaces Frequency initial value.

Dependency

To make this parameter visible, set Output signal frequency source to internal.

Optionally specify an initial frequency in hertz. When you connect to the target, the specified frequency takes effect. It persists until simulation starts, when the value of the frequency signal takes effect. You can use this parameter to specify initial conditions and give them time to stabilize. If no value appears, connecting to the target has no effect on the frequency.

Dependency

To make this parameter visible, set Output signal frequency source to external.

Optionally specify a final frequency in hertz. When simulation is complete, the specified frequency takes effect and persists indefinitely. Disconnecting from the target does not change the frequency. You can use this parameter to put a connected device into a neutral state after simulation. If no value appears, the frequency in effect at the end of simulation persists afterward.

Dependency

To make this parameter visible, set Output signal frequency source to external.

Specify the source that determines the duty cycle. The Output signal duty source can be either of the following:

  • internal (default) — A tunable parameter named Duty specifies the duty cycle.

  • external — A signal specifies the duty cycle. Input port Duty Cycle appears on the block to accept the signal.

Dependency

If you specify internal (the default), Duty is visible. Duty final value is not visible.

If you specify external, port Duty Cycle appears, parameter Duty initial value replaces Duty, and parameter Duty final value is visible.

Specify the duty cycle as a decimal fraction from 0 through 1 inclusive. It determines the amount of time that the output signal value is high (1). For example, a duty cycle of 0.7 specifies that the output is high 70% of the time and low 30% of the time.

Two duty cycle values have special significance:

  • 0 — The output signal is continuously low (0) regardless of the frequency specification currently in effect.

  • 1 — The output signal is continuously high (1) regardless of the frequency specification currently in effect.

Dependency

To make this parameter visible, set Output signal duty source to internal.

Optionally specify an initial duty cycle. When you connect to the target, the specified duty cycle takes effect. It persists until simulation starts. If no value appears, connecting to the target has no effect on the duty cycle. You can specify any duty cycle. Often the Duty initial value is 0 or 1, enforcing a continuously low or high initial output signal. Specifying 0 or 1 overrides any Frequency initial value setting.

Dependency

To make this parameter visible, set Output signal duty source to external.

Optionally specify a final duty cycle. When simulation is complete, the specified duty cycle takes effect and persists indefinitely. Disconnecting from the target does not change the duty cycle. If no value appears, the duty cycle in effect at the end of simulation persists indefinitely afterward. You can specify any duty cycle. Often the Duty final value is 0 or 1, enforcing a continuously low or high initial output signal. Specifying 0 or 1 overrides any Frequency final value setting.

Dependency

To make this parameter visible, set Output signal duty source to external.

Introduced in R2007b

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