Difference
Calculate change in signal over one time step
Libraries:
Simulink /
Discrete
Description
The Difference block outputs the current input value minus the previous input value.
Examples
This example shows how to calculate the difference in a sine wave signal at each time step. The input is a 1-by-2 vector of sine waves, with amplitude 1 and 3. The difference block calculates the difference in each sine wave signal at every time step. The Scope block displays both the original sine waves and the output of the difference block.
Ports
Input
Input signal, specified as a scalar, vector, matrix, or N-D array.
Dependencies
When you set Input processing to
Columns as channels (frame based)
,
the input signal must have two dimensions or less.
Data Types: half
| single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| Boolean
| fixed point
Output
Current input minus previous input, specified as a scalar, vector, matrix, or N-D array.
Data Types: half
| single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| Boolean
| fixed point
Parameters
Main
Set the initial condition for the previous input.
Programmatic Use
Parameter:
ICPrevInput
|
Type: character vector |
Values: scalar | vector | matrix | N-D array |
Default:
'0.0'
|
Specify whether the block performs sample- or frame-based processing:
Columns as channels (frame based)
— Treat each column of the input as a separate channel (frame-based processing).Note
Frame-based processing requires a DSP System Toolbox™ license.
For more information, see Sample- and Frame-Based Concepts (DSP System Toolbox).
Elements as channels (sample based)
— Treat each element of the input as a separate channel (sample-based processing).
Use Input processing to specify whether the block performs sample- or frame-based processing. For more information about these two processing modes, see Sample- and Frame-Based Concepts (DSP System Toolbox).
Programmatic Use
Block Parameter:
InputProcessing |
Type: character vector |
Values: 'Columns as channels
(frame based)' | 'Elements as channels (sample
based)' |
Default: 'Elements as channels
(sample based)' |
Signal Attributes
Lower value of the output range that the software checks.
The software uses the minimum to perform:
Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.
Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).
Automatic scaling of fixed-point data types.
Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).
Tips
Output minimum does not saturate or clip the actual output signal. Use the Saturation block instead.
Programmatic Use
To set the block parameter value programmatically, use
the set_param
function.
Parameter: | OutMin |
Values: | '[]' (default) | scalar in quotes |
Upper value of the output range that the software checks.
The software uses the maximum value to perform:
Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.
Simulation range checking (see Specify Signal Ranges and Enable Simulation Range Checking).
Automatic scaling of fixed-point data types.
Optimization of the code that you generate from the model. This optimization can remove algorithmic code and affect the results of some simulation modes such as SIL or external mode. For more information, see Optimize using the specified minimum and maximum values (Embedded Coder).
Tips
Output maximum does not saturate or clip the actual output signal. Use the Saturation block instead.
Programmatic Use
To set the block parameter value programmatically, use
the set_param
function.
Parameter: | OutMax |
Values: | '[]' (default) | scalar in quotes |
Specify the output data type. You can set it to:
A rule that inherits a data type, for example,
Inherit: Inherit via back propagation
The name of a built-in data type, for example,
single
The name of a data type object, for example, a
Simulink.NumericType
objectAn expression that evaluates to a data type, for example,
fixdt(1,16,0)
The Data Type Assistant helps you set data
attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant.
Dependencies
When input is a floating-point data type smaller than single
precision, the Inherit: Inherit via internal
rule
output data type depends on the setting of
the Inherit floating-point output type smaller than single precision configuration parameter. Data types are smaller than single
precision when the number of bits needed to encode the data type is
less than the 32 bits needed to encode the single-precision data
type. For example, half
and
int16
are smaller than single
precision.
Programmatic Use
Parameter:
OutDataTypeStr
|
Type: character vector |
Values:
'Inherit: Inherit via internal rule' | 'Inherit:
Inherit via back propagation' | 'double' | 'single' | 'int8'
| 'uint8' | 'int16' | 'uint16' | 'int32' | 'uint32' |
'int64' | 'uint64' | 'boolean' | 'fixdt(1,16)' |
'fixdt(1,16,0)' | 'fixdt(1,16,2^0,0)' | '<data type
expression>' |
Default:
'Inherit: Inherit via internal rule'
|
Select this parameter to prevent the fixed-point tools from overriding the Output data type you specify on the block. For more information, see Use Lock Output Data Type Setting (Fixed-Point Designer).
Programmatic Use
To set the block parameter value programmatically, use
the set_param
function.
Parameter: | LockScale |
Values: | 'off' (default) | 'on' |
Specify the rounding mode for fixed-point operations. For more information, see Rounding Modes (Fixed-Point Designer).
Block parameters always round to the nearest representable value. To control the rounding of a block parameter, enter an expression using a MATLAB® rounding function into the mask field.
Programmatic Use
To set the block parameter value programmatically, use
the set_param
function.
Parameter: | RndMeth |
Values: | 'Floor' (default) | 'Ceiling' | 'Convergent' | 'Nearest' | 'Round' | 'Simplest' | 'Zero' |
When you select this check box, overflows saturate to the maximum or minimum value that the data type can represent. Otherwise, overflows wrap.
When you select this check box, saturation applies to every internal operation on the block, not just the output or result. In general, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.
Programmatic Use
Block Parameter:
DoSatur |
Type: character vector |
Values:
'off' | 'on' |
Default:
'off' |
Block Characteristics
Extended Capabilities
The code generator does not explicitly group primitive blocks that constitute a nonatomic masked subsystem block in the generated code. This flexibility allows for more efficient code generation. In certain cases, you can achieve grouping by configuring the masked subsystem block to execute as an atomic unit by selecting the Treat as atomic unit option.
HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.
This block has one default HDL architecture.
ConstrainedOutputPipeline | Number of registers to place at
the outputs by moving existing delays within your design. Distributed
pipelining does not redistribute these registers. The default is
|
InputPipeline | Number of input pipeline stages
to insert in the generated code. Distributed pipelining and constrained
output pipelining can move these registers. The default is
|
OutputPipeline | Number of output pipeline stages
to insert in the generated code. Distributed pipelining and constrained
output pipelining can move these registers. The default is
|
PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.
Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.
Version History
Introduced before R2006a
MATLAB Command
You clicked a link that corresponds to this MATLAB command:
Run the command by entering it in the MATLAB Command Window. Web browsers do not support MATLAB commands.
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: United States.
You can also select a web site from the following list
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)