Conditional Hold

R2026b

Conditionally hold last value

Since R2026b

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  • Conditional Hold block icon

Libraries:
Simulink / Discrete

Description

The Conditional Hold block conditionally holds its input signal u based on the value of the condition signal h. If the input is a vector, the block holds all elements of the vector. The Conditional Hold block inherits its sample time from the input signal.

Comparison with Similar Blocks

The Memory, Unit Delay, Zero-Order Hold, and Conditional Hold blocks provide similar functionality but have different capabilities and purposes.

This table shows recommended usage for each block.

BlockPurposeReference Examples
Unit DelayImplement a delay using a discrete sample time that you specify. The block accepts and outputs signals with a discrete sample time.
MemoryImplement 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 HoldConvert an input signal with a continuous sample time to an output signal with a discrete sample time.
Conditional HoldConditionally holds input signal u based on the value of the condition signal, h. 

This table shows the following capabilities.

CapabilityMemory BlockUnit Delay BlockZero-Order Hold BlockConditional Hold Block
Specification of initial conditionYesYesNo, because the block output at time t = 0 must match the input value.Yes
Specification of sample timeNo, because the block can only inherit sample time from the driving block or the solver used for the entire model.YesYesNo
Support for frame-based signalsNo YesYesNo
Support for state loggingNoYesNoNo

Ports

Input

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Input signal that the block holds.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Hold value condition, specified as one of these values:

  • 1 (true) — The block holds the previously held output value.

  • 0 (false).— The output signal value is the same as the current input signal.

Data Types: Boolean

Output

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Output signal that is the input held depending on the value of h.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus

Parameters

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To edit block parameters interactively, use the Property Inspector. From the Simulink® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Initial block hold value, specified as a scalar value, vector, matrix, or n-dimensional array. If input signal u is a vector, Initial Condition scalar expands.

The Conditional Hold block uses the Initial Condition only at the first time step, when the hold value condition, h, is true (1) and the block has no previous input to hold. Otherwise, the block does not use the Initial Condition.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter: InitialCondition
Values: 0 (default) | scalar | vector | matrix | n-dimensional array
Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | fi | enumerated | bus

Block Characteristics

Data Types

Boolean | bus | double | enumerated | fixed point | half | integer | single

Direct Feedthrough

no

Multidimensional Signals

yes

Variable-Size Signals

yes

Zero-Crossing Detection

yes

Extended Capabilities

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Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced in R2026b

See Also

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