Delay Line

R2026b

Rebuffer sequence of inputs

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Delay Line block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
DSP System Toolbox / Signal Management / Buffers

Description

The Delay Line block rebuffers a sequence of M_i-by-N matrix inputs into a sequence of M_o-by-N matrix outputs, where M_o is the output frame size you specify in the Delay line size parameter. Depending on whether M_o is greater than, less than, or equal to the input frame size, M_i, the output frames can be underlapped or overlapped. The block always performs frame-based processing and rebuffers each of the N input channels independently.

Examples

Rebuffer Signal Using Delay Line

In this example, the Delay Line block rebuffers a signal with frame size 4 to a frame size of 3 using the Delay Line block.

Open the ex_delayline_rebuffer.slx model. The Delay line size parameter is set to 3.

Run the model. The first output frame is all zeros because the Initial conditions parameter is set to zero. Because the input frame size of 4 is larger than the output frame size of 3, only the last three samples in each input frame are propagated to the corresponding output frame. The frame periods of the input and output are the same, and the output sample period is , or 4/3 the input sample period.

Ports

Input

In — Input signal

vector | matrix

Specify the input signal as a vector or a matrix of size M_i-by-N.

This port is unnamed until you select the Show En_Out port for selectively enabling output parameter.

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

En_Out — Linearize the block output

true | false

Specify whether to linearize the block output.

If the input value to the En_Out port is a Boolean 1 (or true), the block linearizes the output and the output is valid. This setting allows the block to be more efficient when the tapped Delay Line output is not required at each sample time.

Note that when the input value to the En_Out port is a Boolean 0 (or false), the block can give different results depending on the state of the model. The results can appear to match valid results or can be invalid, and they cannot be predicted. You should ignore the block output in all cases when the input to the En_Out port is 0.

Dependencies

To enable this port, select the Show En_Out port for selectively enabling output parameter.

Data Types: Boolean

Output

Out — Rebuffered output

vector | matrix

Rebuffered output, returned as a vector or a matrix of size M_o-by-N.

When M_o > M_i, the output frame overlap is the difference between the output and input frame size, M_o−M_i. When M_o < M_i, the output is underlapped and the Delay Line block discards the first M_i−M_o samples of each input frame so that only the last M_o samples are buffered into the corresponding output frame. When M_o = M_i, the output data is identical to the input data, but is delayed by the latency of the block. Due to the block latency, the outputs are always delayed by one frame, the entries of which you specify in the Initial conditions parameter.

The output frame period is equal to the input frame period (T_fo=T_fi). The output sample period, T_so, is therefore equal to T_fi/M_o, or equivalently, T_si(M_i/M_o)

In the most typical use, each output differs from the preceding output by only one sample, as illustrated below for scalar input.

Note that the first output of the block in the example above is all zeros; this is because the Initial Conditions parameter is set to zero.

This port is unnamed until you select the Show En_Out port for selectively enabling output parameter.

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

Parameters

Delay line size — Delay line size

64 (default) | positive integer

Specify the number of rows M_o in output matrix as a positive integer.

Initial conditions — Initial conditions

0 (default) | scalar | vector | matrix

Specify the value of the block initial output as a scalar, vector, or a matrix. The Delay Line block buffer is initialized to the value specified by the Initial conditions parameter. The block outputs this buffer at the first simulation step (t=0).

When the block outputs a vector, the Initial conditions can be a vector of the same size, or a scalar value to be repeated across all elements of the initial output. When the block outputs a matrix, the Initial conditions can be a matrix of the same size, a vector (of length equal to the number of matrix rows) to be repeated across all columns of the initial output, or a scalar to be repeated across all elements of the initial output.

Allow directfeedthrough — Allow direct feed through

off (default) | on

When you select this check box, the input data is not delayed by an extra frame before it is available at the output buffer. Instead, the input data is available immediately at the output port of the block.

Show En_Out port for selectively enabling output — Show En_Out port for selectively enabling output

off (default) | on

When you select this check box, the En_Out input port appears on the block icon. This block uses a circular buffer internally even though the output is linear. This means that for valid output, data from the circular buffer has to be linearized. The En_Out port determines whether or not a valid output needs to be computed based on the value of its Boolean input. If the input value to the En_Out port is 1, the block output is linearized, and thus is valid. Otherwise, the output is not linearized, and is invalid. This allows the block to be more efficient when the tapped Delay Line output is not required at each sample time.

Note that when the input value to the En_Out port is 0, the block can give different results depending on the state of the model. The results can appear to match valid results or can be invalid, and they cannot be predicted. You should ignore the block output in all cases when the input to the En_Out port is 0.

Hold previous value when the output is disabled — Hold previous value when the output is disabled

off (default) | on

Use this parameter to specify the block output at those time steps when the internal state buffer is not being linearized to output valid data.

When you do not select this check box, the block memory is free to be used by other parts of the model, and the signal on the output port is invalid. When you select this check box, the most recent valid value is held on the output port, and slightly more memory is used by the block.

Dependencies

To enable this parameter, select Show En_Out port for selectively enabling output.

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"dspbuff3/Delay Line"

Example: add_block("dspbuff3/Delay Line","myModel/myBlock",MakeNameUnique="on")

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Generated code relies on the memcpy or memset function (string.h) under certain conditions.

Version History

Introduced before R2006a