Implement zero-order hold of one sample period
The Zero-Order Hold block holds its input for the sample period you specify. The block accepts one input and generates one output. Each signal can be scalar or vector. If the input is a vector, the block holds all elements of the vector for the same sample period.
You specify the time between samples with the Sample
time parameter. A setting of
the block inherits the Sample time.
Tip Do not use the Zero-Order Hold block to create a fast-to-slow transition between blocks operating at different sample rates. Instead, use the Rate Transition block.
The Unit Delay, Memory, and Zero-Order Hold blocks provide similar functionality but have different capabilities. Also, the purpose of each block is different. The sections that follow highlight some of these differences.
|Block||Purpose of the Block||Reference Examples|
|Unit Delay||Implement a delay using a discrete sample time that you specify. The block accepts and outputs signals with a discrete sample time.|
|Memory||Implement a delay by one major integration time step. Ideally, the block accepts continuous (or fixed in minor time step) signals and outputs a signal that is fixed in minor time step.|
|Zero-Order Hold||Convert an input signal with a continuous sample time to an output signal with a discrete sample time.|
|Unit Delay||Memory||Zero-Order Hold|
|Specification of initial condition||Yes||Yes||No, because the block output at time t = 0 must match the input value.|
|Specification of sample time||Yes||No, because the block can only inherit sample time (from the driving block or the solver used for the entire model).||Yes|
|Support for frame-based signals||Yes||No||Yes|
|Support for state logging||Yes||No||No|
The Zero-Order Hold block accepts real or complex signals of any data type that Simulink® supports, including fixed-point and enumerated data types.
For more information, see Data Types Supported by Simulink in the Simulink documentation.
Specify the time interval between samples. To inherit the sample
time, set this parameter to
-1. See Specify Sample Time in
the online documentation for more information.
Do not specify a continuous sample time, either
This block supports only discrete sample times. When this parameter
-1, the inherited sample time must be discrete
and not continuous.
The Zero-Order Hold block is a bus-capable block. The input can be a virtual or nonvirtual bus signal. No block-specific restrictions exist. All signals in a nonvirtual bus input to a Zero-Order Hold block must have the same sample time, even if the elements of the associated bus object specify inherited sample times. You can use a Rate Transition block to change the sample time of an individual signal, or of all signals in a bus. See Specify Bus Signal Sample Times and Bus-Capable Blocks for more information.
You can use an array of buses as an input signal to a Zero-Order Hold block. For details about defining and using an array of buses, see Combine Buses into an Array of Buses.
Double | Single | Boolean | Base Integer | Fixed-Point | Enumerated | Bus
Specified in the Sample time parameter