Simulink Reference

Switch

Switch output between the first input and the third input based on the value of the second input

Library

Signal Routing

Description

The Switch block passes through the first (top) input or the third (bottom) input based on the value of the second (middle) input. The first and third inputs are called data inputs. The second input is called the control input.

You select the conditions under which the first input is passed with the Criteria for passing first input parameter. You can make the block check whether the control input is greater than or equal to the threshold value, purely greater than the threshold value, or nonzero. If the control input meets the condition set in the Criteria for passing first input parameter, then the first input is passed. Otherwise, the third input is passed.

Note    If the data inputs to the switch are buses, the element names of both buses must be the same to ensure that the output bus has the same element names no matter which input bus is selected. You can ensure that your model meets this requirement by using a bus object to define the buses with the model's Element name mismatch diagnostic set to error. See Connectivity Diagnostics for more information.

Data Type Support

The data and control inputs of a Switch block accept real or complex signals of any data type supported by Simulink, including fixed-point data types.

For a discussion on the data types supported by Simulink, refer to Data Types Supported by Simulink in the Using Simulink documentation.

Parameters and Dialog Box

The Main pane of the Switch block dialog appears as follows:

Criteria for passing first input

Select the conditions under which the first input is passed. You can make the block check whether the control input is greater than or equal to the threshold value, purely greater than the threshold value, or nonzero. If the control input meets the condition set in this parameter, then the first input is passed. Otherwise, the third input is passed.

Threshold

Assign the switch threshold that determines which input is passed to the output.

Enable zero crossing detection

Select to enable zero crossing detection. For more information, see Zero Crossing Detection in the Using Simulink documentation.

Sample time (-1 for inherited)

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. See Specifying Sample Time in the online documentation for more information.

The Signal data types pane of the Switch block dialog appears as follows:

Require all data port inputs to have same data type

Select to require all data inputs to have the same data type.

Output data type mode

Choose to inherit the output data type and scaling by backpropagation or by an internal rule. The internal rule causes the output of the block to have the same data type and scaling as the input with the larger positive range.

Round integer calculations toward

Select the rounding mode for fixed-point operations.

Saturate on integer overflow

Select to have overflows saturate.

Characteristics

Direct Feedthrough	Yes
Sample Time	Specified in the Sample time parameter
Scalar Expansion	Yes
Dimensionalized	Yes
Zero Crossing	Yes, if enabled

See Also

Multiport Switch

Sum of Elements

Switch Case

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