Compute discretetime derivative
Simulink / Discrete
The Discrete Derivative block computes an optionally scaled discrete time derivative as follows
$$y({t}_{n})=K\left(\frac{u({t}_{n})u({t}_{n1})}{{T}_{s}}\right)$$
where
$$u({t}_{n})$$ and $$y({t}_{n})$$ are the block input and output at the current time step, respectively.
$$u({t}_{n1})$$ is the block input at the previous time step.
$$K$$ is an optional scaling factor, specified using the Gain value parameter.
$${T}_{s}$$ is the simulation's discrete step size, which must be fixed.
Do not use this block in subsystems with a nonperiodic trigger (for example, nonperiodic functioncall subsystems). This configuration produces inaccurate results.
Port_1
— Input signalInput signal, specified as a scalar, vector, or matrix.
Data Types: single
 double
 int8
 int16
 int32
 uint8
 uint16
 uint32
 fixed point
Port_1
— Scaled discrete time derivativeOptionally scaled discretetime derivative, specified as a scalar, vector, or matrix. For more information on how the block computes the discretetime derivative, see Description. You specify the data type of the output signal with the Output data type parameter.
Data Types: single
 double
 int8
 int16
 int32
 uint8
 uint16
 uint32
 fixed point
Gain value
— Scaling factor1.0
(default)  scalarScaling factor applied to the computed derivative, specified as a real scalar value.
Block Parameter:
gainval

Type: character vector 
Values: scalar 
Default:
'1.0'

Initial condition for previous weighted input K*u/Ts
— Initial condition0.0
(default)  scalarInitial condition for the previous scaled input, specified as a scalar.
Block Parameter:
ICPrevScaledInput

Type: character vector 
Values: scalar 
Default:
'0.0'

Input processing
— Specify sample or framebased processingElements as channels (sample based)
(default)  Columns as channels (frame based)
Specify whether the block performs sample or framebased processing:
Columns as channels (frame based)
— Treat
each column of the input as a separate channel (framebased processing).
Framebased processing requires a DSP System Toolbox™ license.
For more information, see Sample and FrameBased Concepts (DSP System Toolbox).
Elements as channels (sample based)
— Treat
each element of the input as a separate channel (samplebased
processing).
Use Input processing to specify whether the block performs
sample or framebased processing. The block accepts framebased signals for the input
u
. All other input signals must be samplebased.
Input Signal u  Input Processing Mode  Block Works? 

Sample based  Sample based  Yes 
Frame based  No, produces an error  
Sample based  Frame based  Yes 
Frame based  Yes 
For more information about these two processing modes, see Sample and FrameBased Concepts (DSP System Toolbox).
Block Parameter:
InputProcessing 
Type: character vector 
Values: 'Columns as channels
(frame based)'  'Elements as channels (sample
based)' 
Default: 'Elements as channels
(sample based)' 
Output minimum
— Minimum output value for range checking[]
(default)  scalarLower value of the output range that Simulink^{®} checks.
Simulink uses the minimum to perform:
Parameter range checking (see Specify Minimum and Maximum Values for Block Parameters) for some blocks.
Simulation range checking (see Signal Ranges and Enable Simulation Range Checking).
Automatic scaling of fixedpoint 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 (Simulink Coder).
Output minimum does not saturate or clip the actual output signal. Use the Saturation block instead.
Block Parameter:
OutMin 
Type: character vector 
Values: '[ ]' 
scalar 
Default: '[ ]' 
Output maximum
— Maximum output value for range checking[]
(default)  scalarUpper value of the output range that Simulink checks.
Simulink 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 Signal Ranges and Enable Simulation Range Checking).
Automatic scaling of fixedpoint 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 (Simulink Coder).
Output maximum does not saturate or clip the actual output signal. Use the Saturation block instead.
Block Parameter:
OutMax 
Type: character vector 
Values: '[ ]' 
scalar 
Default: '[ ]' 
Output data type
— Output data typeInherit: Inherit via internal
rule
(default)  Inherit: Inherit via back
propagation
 double
 single
 int8
 uint8
 int16
 uint16
 int32
 uint32
 int64
 uint64
 fixdt(1,16,0)
 fixdt(1,16,2^0,0)
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 builtin data type, for example,
single
The name of a data type object, for example, a
Simulink.NumericType
object
An expression that evaluates to a data type, for example,
fixdt(1,16,0)
Click the Show data type assistant button to display the Data Type Assistant, which helps you set the data type attributes. For more information, see Specify Data Types Using Data Type Assistant.
Block 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'  'fixdt(1,16,0)' 
'fixdt(1,16,2^0,0)' 
Default:
'Inherit: Inherit via internal rule'

Lock output data type setting against changes by the fixedpoint tools
— Prevent fixedpoint tools from overriding Output data typeoff
(default)  on
Select this parameter to prevent the fixedpoint tools from overriding the Output data type you specify on the block. For more information, see Use Lock Output Data Type Setting (FixedPoint Designer).
Block Parameter:
LockScale 
Type: character vector 
Values:
'off'  'on' 
Default:
'off' 
Integer rounding mode
— Rounding mode for fixedpoint operationsFloor
(default)  Ceiling
 Convergent
 Nearest
 Round
 Simplest
 Zero
Specify the rounding mode for fixedpoint operations. For more information, see Rounding (FixedPoint 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.
Block Parameter:
RndMeth 
Type: character vector 
Values:
'Ceiling'  'Convergent'  'Floor'  'Nearest'  'Round'  'Simplest' 
'Zero' 
Default:
'Floor' 
Saturate to max or min when overflows occur
— Method of overflow actionoff
(default)  on
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.
Block Parameter:
DoSatur 
Type: character vector 
Values:
'off'  'on' 
Default:
'off' 
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 

Depends on absolute time when used inside a triggered subsystem hierarchy.
Generated code relies on memcpy
or
memset
functions (string.h
) under
certain conditions.
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