DSP Blockset

Sample and Hold

Sample and hold an input signal.

Library

Signal Operations

Description

The Sample and Hold block acquires the input at the signal port whenever it receives a trigger event at the trigger port (marked by ). The block then holds the output at the acquired input value until the next triggering event occurs. If the acquired input is frame-based, the output is frame-based; otherwise, the output is sample-based.

The trigger input must be a sample-based scalar with sample rate equal to the input frame rate at the signal port. The trigger event is specified by the Trigger type pop-up menu, and can be one of the following:

• Rising edge triggers the block to acquire the signal input when the trigger input rises from a negative value or zero to a positive value.
• Falling edge triggers the block to acquire the signal input when the trigger input falls from a positive value or zero to a negative value.
• Either edge triggers the block to acquire the signal input when the trigger input either rises from a negative value or zero to a positive value or falls from a positive value or zero to a negative value.

The block's output prior to the first trigger event is specified by the Initial condition parameter. If the acquired input is an M-by-N matrix, the Initial condition can be an M-by-N matrix, or a scalar to be repeated across all elements of the matrix. If the input is a length-M 1-D vector, the Initial condition can be a length-M row or column vector, or a scalar to be repeated across all elements of the vector.

Dialog Box

Trigger type

The type of event that triggers the block to acquire the input signal.

Initial condition

The block's output prior to the first trigger event.

Supported Data Types

• Double-precision floating point
• Single-precision floating point
• Fixed-point
• Custom data types
• Boolean
• 8-, 16-, and 32-bit signed integers
• 8-, 16-, and 32-bit unsigned integers

To learn how to convert to the above data types in MATLAB and Simulink, see Supported Data Types and How to Convert to Them.

See Also

Downsample	DSP Blockset
N-Sample Switch	DSP Blockset

Also see Signal Operations for a list of all the blocks in the Signal Operations library.

RMS

Short-Time FFT