Triggered Signal From Workspace (DSP Blockset)

Acquire and output a workspace signal when triggered.

Library

DSP Sources

Description

The Triggered Signal From Workspace block references a specified vector or matrix in the MATLAB workspace to generate scalar, vector, or matrix output. Each element of a workspace vector, and each row of a workspace matrix is considered to be individual sample. (Matrix columns represent independent channels.)

The block acquires and outputs a frame of M new samples from the specified workspace variable each time it is triggered by the control signal at the input port. The output frame size, M, is specified in the block dialog by the Samples per frame parameter. When the Samples per frame parameter is set to 1, the block acquires and outputs a single sample (a vector element or matrix row) each time it is triggered.

For a W-by-N workspace matrix, the output size is M-by-N, with each column representing a distinct signal channel. For example, if the Signal parameter references a W-by-4 workspace matrix and the Samples per frame parameter is set to 6, the block generates a sequence of 6-by-4 matrices, as illustrated below. Each matrix contains six consecutive samples from four distinct channels

Note, however, that a 1-by-N matrix (row vector) is treated as a N-by-1 matrix (column vector), and acquired element-wise rather than row-wise.

Trigger Event

The triggering event at the input is specified by the Trigger type pop-up menu, and can be one of the following:

Rising edge triggers execution of the block when the trigger input rises from a negative value to zero or a positive value, or from zero to a positive value.
Falling edge triggers execution of the block when the trigger input falls from a positive value to zero or a negative value, or from zero to a negative value.
Either edge triggers execution of the block when either a rising or falling edge (as described above) occurs.

Initial and Final Conditions

The Initial output parameter specifies the output of the block from the start of the simulation until the first trigger arrives. Subsequently, the block holds the output value constant (at its last value) between trigger events. For vector signals, the Initial output parameter value can be a vector of length M or a scalar to copy across the M elements of the initial frame. For matrix signals, the Initial output parameter value can be a vector of length N to copy across the M rows of the initial output, or a scalar to copy across the M*N elements of the initial output.

When the block has output all of the signal samples, it can start again with the beginning of the signal or simply output zeros (or zero-vectors or zero-matrices, as appropriate) until the end of the simulation.

If the Output signal repeatedly check box is selected, when the block outputs the last frame of the signal, it returns to the beginning of the signal to repeat the process. If there are not enough samples at the end of the signal to fill the final frame, the last frame is zero-padded as necessary. This ensures that the block's output for each cycle is identical (e.g., the third frame of one cycle contains the same data as the third frame of any other cycle).
If the Output signal repeatedly check box is not selected, when the block outputs the last frame of the signal, it continues outputting frames of zeros for the duration of the simulation.

Dialog Box

Signal: The name of the workspace vector or matrix from which to acquire data, or a valid MATLAB expression.
Trigger type: The type of event that triggers the block's execution. This parameter is not tunable in Simulink's external mode.
Output signal repeatedly: Specifies continuous (repeating) operation or one-time operation.
Initial output: The value to output until the first trigger event is received. This parameter is not tunable in Simulink's external mode.
Samples per frame: The number of input samples (vector elements or matrix rows) to acquire into each output frame, M.