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The Constant block generates a real or complex constant value. The block generates scalar, vector, or matrix output, depending on the dimensionality of the Constant value parameter and the setting of the Interpret vector parameters as 1-D parameter. Also, the block can generate either a sample-based or frame-based signal, depending on the setting of the Sampling mode parameter.
The output of the block has the same dimensions and elements as the Constant value parameter. If you specify a vector for this parameter, and you want the block to interpret it as a vector, select the Interpret vector parameters as 1-D parameter. Otherwise, the block treats the Constant value parameter as a matrix.
By default, the Constant block outputs a signal whose data type and complexity are the same as that of the block's Constant value parameter. However, you can specify the output to be any data type supported by Simulink software, including fixed-point and enumerated data types. The Enumerated Constant block may be more convenient than the Constant block for outputting a constant enumerated value.
For a discussion on the data types supported by Simulink software, see Data Types Supported by Simulink.
The Main pane of the Constant block dialog box appears as follows:
Opening this dialog box causes a running simulation to pause. See Changing Source Block Parameters During Simulation.
The Signal Attributes pane of the Constant block dialog appears as follows:
Display the Data Type Assistant.
The Data Type Assistant helps you set the Output data type parameter.
See Specifying Block Output Data Types for more information.
See Block-Specific Parameters for the command-line information.
Specify the constant value output of the block.
Default: 1
Minimum: value from the Output minimum parameter
Maximum: value from the Output maximum parameter
You can enter any expression that MATLAB evaluates as a matrix, including the Boolean keywords true and false.
This parameter is converted from its data type to the specified output data type offline using round toward nearest and saturation.
See Block-Specific Parameters for the command-line information.
Select this check box to output a vector of length N if the Constant value parameter evaluates to an N-element row or column vector.
Default: On
On Outputs a vector of length N if the Constant value parameter evaluates to an N-element row or column vector. For example, the block outputs a matrix of dimension 1-by-N or N-by-1.
OffDoes not output a vector of length N if the Constant value parameter evaluates to an N-element row or column vector.
If you clear this check box, you can interact with the Sampling mode parameter.
This parameter enables Sampling mode.
See Block-Specific Parameters for the command-line information.
Specify whether the output signal is Sample based or Frame based.
Default: Sample based
To generate frame-based signals, you must have the Signal Processing Blockset™ product installed.
For more information, see Sample-Based Signals and Frame-Based Signals in the Signal Processing Blockset User's Guide.
Clearing Interpret vector parameters as 1-D enables this parameter.
Selecting Sample based enables the following parameter:
Sample time
Selecting Frame based enables the following parameter:
Frame period
See Block-Specific Parameters for the command-line information.
Specify the interval between times that the Constant block output can change during simulation (for example, due to tuning the Constant value parameter).
Default: inf
This setting indicates that the block output can never change. This setting speeds simulation and generated code by avoiding the need to recompute the block output.
See How to Specify the Sample Time in the online documentation for more information.
Sampling mode enables this parameter.
See Block-Specific Parameters for the command-line information.
Specify the interval between frames that the Constant block output can change during simulation (for example, due to tuning the Constant value parameter).
Default: inf
Sampling mode enables this parameter.
See Block-Specific Parameters for the command-line information.
Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor.
Default: Off
OnLocks the output data type setting for this block.
OffAllows the Fixed-Point Tool and the Fixed-Point Advisor to change the output data type setting for this block.
See Block-Specific Parameters for the command-line information.
For more information, see Fixed-Point Tool and Fixed-Point Advisor in the Simulink Fixed Point documentation.
Specify the minimum value that the block should output.
Default: []
The default value, [], is equivalent to -Inf.
Simulink software uses this value to perform:
Parameter range checking (see Checking Parameter Values) for some blocks
Simulation range checking (see Checking Signal Ranges)
Automatic scaling of fixed-point data types
This number must be a double scalar value.
See Block-Specific Parameters for the command-line information.
Specify the maximum value that the block should output.
Default: []
The default value, [], is equivalent to Inf.
Simulink software uses this value to perform:
Parameter range checking (see Checking Parameter Values) for some blocks
Simulation range checking (see Checking Signal Ranges)
Automatic scaling of fixed-point data types
This number must be a double scalar value.
See Block-Specific Parameters for the command-line information.
Specify the output data type.
Default: Inherit: Inherit via internal rule (Discrete-Time Integrator, Gain, Product, Sum, Switch block), Inherit: Inherit from 'Constant value' (Constant block), Inherit: Inherit via back propagation (Data Type Conversion block), Inherit: Same as input (Saturation block)
This option appears for some blocks. Simulink software chooses a combination of output scaling and data type that requires the smallest amount of memory consistent with accommodating the calculated output range and maintaining the output precision of the block and with the word size of the targeted hardware implementation specified for the model. If the Device type parameter on the Hardware Implementation configuration parameters pane is set to ASIC/FPGA, Simulink software chooses the output data type without regard to hardware constraints. Otherwise, Simulink software chooses the smallest available hardware data type capable of meeting the range and precision constraints. For example, if the block multiplies an input of type int8 by a gain of int16 and ASIC/FPGA is specified as the targeted hardware type, the output data type is sfix24. If Unspecified (assume 32-bit Generic), i.e., a generic 32-bit microprocessor, is specified as the target hardware, the output data type is int32. If none of the word lengths provided by the target microprocessor can accommodate the output range, Simulink software displays an error message in the Simulation Diagnostics Viewer.
Use data type of Constant value parameter. This option appears for some blocks.
Use data type of the driving block.
Use data type of sole input signal. This option appears for some blocks.
Use data type of first input signal. This option appears for some blocks.
Output data type is the same as accumulator data type. This option appears for some blocks.
Output data type is double.
Output data type is single.
Output data type is int8.
Output data type is uint8.
Output data type is int16.
Output data type is uint16.
Output data type is int32.
Output data type is unt32.
Output data type is fixed point fixdt(1,16,0).
Output data type is fixed point fixdt(1,16,2^0,0).
Use an enumerated data type, for example, Enum: BasicColors. This option appears for some blocks.
Use a data type object, for example, Simulink.NumericType.
See Block-Specific Parameters for the command-line information.
See Specifying Block Output Data Types in the Simulink User's Guide for more information.
Select the category of data to specify.
Default: Inherit (Constant, Data Type Conversion, Discrete Time Integrator, Gain, Inport, Outport, Product, Saturation, Sum, Switch), Built in (Logical Operator, Relational Operator)
Inheritance rules for data types. Selecting Inherit enables a second menu/text box to the right. The following list is the possible values, which can vary by block:
Inherit from 'Constant value' (Constant block default)
Inherit via internal rule (Discrete-Time Integrator, Gain, Product, Sum, Switch block default)
Inherit via back propogation (Data Type Conversion block default)
auto (Inport, Outport block default)
Logical (see Configuration Parameters: Optimization)
Same as first input
Same as input (Saturation block default)
Same as accumulator
Built-in data types. Selecting Built in enables a second menu/text box to the right. The following list is the possible values, which can vary by block:
double (Constant, Data Type Conversion, Discrete-Time Integrator, Gain, Inport, Outport, Product, Saturation, Sum, Switch block default)
single
int8
uint8
int16
uint16
int32
uint32
boolean (Logical Operator, Relational Operator block default)
Fixed-point data types.
Enumerated data types. This option is available on some blocks. Selecting Enumerated enables a second menu/text box to the right. The following list is the possible values, which can vary by block:
<class name>
Expressions that evaluate to data types. Selecting Expression enables a second menu/text box to the right. The following list is the possible values, which can vary by block:
<data type expression>
Clicking the Show data type assistant button enables this parameter.
See Block-Specific Parameters for the command-line information.
See Using the Data Type Assistant in the Simulink User's Guide.
Specify whether you want the fixed-point data as signed or unsigned.
Default: Signed
Selecting Mode > Fixed point enables this parameter.
See Block-Specific Parameters for the command-line information.
See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.
Specify the bit size of the word that holds the quantized integer.
Default: 16
Minimum: 0
Maximum: 32
Large word sizes represent large values with greater precision than small word sizes.
Selecting Mode > Fixed point enables this parameter.
See Block-Specific Parameters for the command-line information.
See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.
Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors.
Default: Best precision (Constant), Binary point (Data Type Conversion, Discrete-Time Integrator, Gain, Inport, Outport, Product, Saturation, Sum, Switch), Integer (Logical Operator, Relational Operator)
Specify binary point location.
Enter slope and bias.
Specify best-precision values. This option appears for some blocks.
Specify integer. This setting has the same result as specifying a binary point location and setting fraction length to 0. This option appears for some blocks.
Selecting Mode > Fixed point enables this parameter.
Selecting Binary point enables:
Fraction length
Calculate Best-Precision Scaling
Selecting Slope and bias enables:
Slope
Bias
Calculate Best-Precision Scaling
See Block-Specific Parameters for the command-line information.
See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.
Specify fraction length for fixed-point data type.
Default: 0
Binary points can be positive or negative integers.
Selecting Scaling > Binary point enables this parameter.
See Block-Specific Parameters for the command-line information.
See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.
Specify slope for the fixed-point data type.
Default: 2^0
Specify any positive real number.
Selecting Scaling > Slope and bias enables this parameter.
See Block-Specific Parameters for the command-line information.
See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.
Specify bias for the fixed-point data type.
Default: 0
Specify any real number.
Selecting Scaling > Slope and bias enables this parameter.
See Block-Specific Parameters for the command-line information.
See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.
Direct Feedthrough | N/A |
Sample Time | Specified in the Sample time parameter |
Scalar Expansion | No |
Dimensionalized | Yes |
Multidimensionalized | Yes |
Zero-Crossing Detection | No |
 | Configurable Subsystem | Coulomb and Viscous Friction |  |
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