Data Type Conversion

Convert input signal to specified data type

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Libraries:
Simulink / Commonly Used Blocks
Simulink / Signal Attributes
HDL Coder / Commonly Used Blocks
HDL Coder / HDL Floating Point Operations
HDL Coder / Signal Attributes

Description

The Data Type Conversion block converts an input signal of any Simulink^® data type to the data type that you specify.

Note

To control the output data type by specifying block parameters, or to inherit a data type from a downstream block, use the Data Type Conversion block. To inherit a data type from a different signal in the model, use the Data Type Conversion Inherited block.

Convert Fixed-Point Signals

When you convert between fixed-point data types, the Input and output to have equal parameter controls block behavior. This parameter does not change the behavior of the block when:

• The input and output do not have a fixed-point data type.

• The input or output has a fixed-point data type with trivial scaling.

For more information about fixed-point numbers, see Fixed-Point Numbers in Simulink (Fixed-Point Designer).

To convert a signal from one data type to another by attempting to preserve the real-world value of the input signal, select Real World Value (RWV), the default setting. The block accounts for the limits imposed by the scaling of the input and output and attempts to generate an output of equal real-world value.

To change the real-world value of the input signal by performing a scaling reinterpretation of the stored integer value, select Stored Integer (SI). Within the limits of the specified data types, the block attempts to preserve the stored integer value of the signal during conversion. A best practice is to specify input and output data types using the same word length and signedness. Doing so ensures that the block changes only the scaling of the signal. Specifying a different signedness or word length for the input and output could produce unexpected results such as range loss or unexpected sign extensions. For an example, see Convert Data Types in Simulink Models.

If you select Stored Integer (SI), the block does not perform a lower-level bit reinterpretation of a floating-point input signal. For example, if the input is single and has value 5, the bits that store the input in memory are given in hexadecimal by the following command.

num2hex(single(5))

40a00000

However, the Data Type Conversion block does not treat the stored integer value as 40a00000, but instead as the real-world value, 5. After conversion, the stored integer value of the output is 5.

Cast Enumerated Signals

Use a Data Type Conversion block to cast enumerated signals as follows:

1. To cast a signal of enumerated type to a signal of any numeric type.

   The underlying integers of all enumerated values input to the Data Type Conversion block must be within the range of the numeric type. Otherwise, an error occurs during simulation.

2. To cast a signal of any integer type to a signal of enumerated type.

   The value input to the Data Type Conversion block must match the underlying value of an enumerated value. Otherwise, an error occurs during simulation.

   You can enable the Saturate on integer overflow parameter so that Simulink uses the default value of the enumerated type when the value input to the block does not match the underlying value of an enumerated value. See Type Casting for Enumerations (Simulink Coder).

You cannot use a Data Type Conversion block in these cases:

• To cast a noninteger numeric signal to an enumerated signal.

• To cast a complex signal to an enumerated signal, regardless of the data types of the real and imaginary parts of the complex signal.

See Simulink Enumerations for information on working with enumerated types.

Examples

Convert Data Types in Simulink Models

This example shows three different methods of converting data types in your model using the Data Type Conversion and Data Type Conversion Inherited blocks. In this model, a Sine Wave block generates the input signal. The Sine Wave block only outputs double-precision data types, so to generate a sine wave with a data type of single, you must perform a data type conversion.

In the first row, the Data Type Conversion Inherited block uses the data type coming from the Constant block (single) as the reference data type, and converts the sine wave to single.

In the second row, the Data Type Conversion block has the Output data type set to single, and the sine wave is converted accordingly.

In the third row, the Data Type Conversion1 block has the Output data type set to Inherit: Inherit via back propagation. Because the downstream Gain2 block has a data type of single, the Data Type Conversion1 block converts the sine wave to a data type of single.

Ports

Input

Port_1 — Input signal

scalar | vector | matrix | N-D array

Input signal, specified as a scalar, vector, matrix, or N-D array. The input can be any real- or complex-valued signal. If the input is real, the output is real. If the input is complex, the output is complex. The block converts the input signal to the Output data type you specify.

When you are converting fixed-point data types, use the Input and output to have equal parameter to determine whether the conversion happens based on the Real World Value (RWV) or Stored Integer (SI) value of the signal. For more information, see Convert Fixed-Point Signals.

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

Output

Port_1 — Output signal

scalar | vector | matrix | N-D array

Output signal, converted to the data type you specify, with the same dimensions as the input signal.

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

Parameters

Output minimum — Minimum output value for range checking

[] (default) | scalar

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

Output maximum — Maximum output value for range checking

[] (default) | scalar

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

Output data type — Output data type

Inherit: Inherit via back propagation (default) | double | single | half | int8 | uint8 | int16 | uint16 | int32 | uint32 | int64 | uint64 | boolean | fixdt(1,16) | fixdt(1,16,0) | fixdt(1,16,2^0,0) | Enum: <class name> | <data type expression>

Choose the data type for the output. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

Programmatic Use

Block Parameter: OutDataTypeStr

Type: character vector

Values: 'Inherit: Inherit via back propagation' | 'double' | 'single' | 'half' | 'int8' | 'uint8' | 'int16' | 'uint16' | 'int32' | 'uint32' | 'int64' | 'uint64' | 'fixdt(1,16)' | 'fixdt(1,16,0)' | 'fixdt(1,16,2^0,0)' | 'Enum: <class name>' | '<data type expression>'

Default: 'Inherit: Inherit via back propagation'

Lock output data type setting against changes by the fixed-point tools — Option to prevent fixed-point tools from overriding Output data type

off (default) | on

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'

Input and output to have equal — Constraint for converting fixed-point data types

Real World Value (RWV) (default) | Stored Integer (SI)

Specify which type of input and output must be equal, in the context of fixed-point data representation.

• Real World Value (RWV) — Specifies the goal of making the Real World Value (RWV) of the input equal to the Real World Value (RWV) of the output.

• Stored Integer (SI) — Specifies the goal of making the Stored Integer (SI) value of the input equal to the Stored Integer (SI) value of the output.

Programmatic Use

Block Parameter: ConvertRealWorld

Type: character vector

Values: 'Real World Value (RWV)' | 'Stored Integer (SI)'

Default: 'Real World Value (RWV)'

Integer rounding mode — Specify the rounding mode for fixed-point operations

Floor (default) | Ceiling | Convergent | Nearest | Round | Simplest | Zero

Choose one of these rounding modes.

Ceiling

Rounds both positive and negative numbers toward positive infinity. Equivalent to the MATLAB^® ceil function.

Convergent

Rounds number to the nearest representable value. If a tie occurs, rounds to the nearest even integer. Equivalent to the Fixed-Point Designer™ convergent function.

Floor

Rounds both positive and negative numbers toward negative infinity. Equivalent to the MATLAB floor function.

Nearest

Rounds number to the nearest representable value. If a tie occurs, rounds toward positive infinity. Equivalent to the Fixed-Point Designer nearest function.

Round

Rounds number to the nearest representable value. If a tie occurs, rounds positive numbers toward positive infinity and rounds negative numbers toward negative infinity. Equivalent to the Fixed-Point Designer round function.

Simplest

Automatically chooses between round toward floor and round toward zero to generate rounding code that is as efficient as possible.

Zero

Rounds number toward zero. Equivalent to the MATLAB fix function.

Programmatic Use

Block Parameter: RndMeth

Type: character vector

Values: 'Ceiling' | 'Convergent' | 'Floor' | 'Nearest' | 'Round' | 'Simplest' | 'Zero'

Default: 'Floor'

See Also

For more information, see Rounding Modes (Fixed-Point Designer).

Saturate on integer overflow — Method of overflow action

off (default) | on

Specify whether overflows saturate or wrap.

• on — Overflows saturate to either the minimum or maximum value that the data type can represent.

• off — Overflows wrap to the appropriate value that the data type can represent.

For example, the maximum value that the signed 8-bit integer int8 can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer.

• With this parameter selected, the block output saturates at 127. Similarly, the block output saturates at a minimum output value of -128.

• With this parameter cleared, the software interprets the overflow-causing value as int8, which can produce an unintended result. For example, a block result of 130 (binary 1000 0010) expressed as int8 is -126.

Tips

• Consider selecting this parameter when your model has a possible overflow and you want explicit saturation protection in the generated code.

• Consider clearing this parameter when you want to optimize efficiency of your generated code. Clearing this parameter also helps you to avoid overspecifying how a block handles out-of-range signals. For more information, see Troubleshoot Signal Range Errors.

• When you select this parameter, 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

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

Parameter:	SaturateOnIntegerOverflow
Values:	'off' (default) | 'on'

Sample time (-1 for inherited) — Interval between samples

-1 (default) | scalar | vector

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. For more information, see Specify Sample Time.

Dependencies

This parameter is visible only if you set it to a value other than -1. To learn more, see Blocks for Which Sample Time Is Not Recommended.

Programmatic Use

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

Parameter:	SampleTime
Values:	"-1" (default) | scalar or vector in quotes

Mode — Select data type mode

Inherit (default) | Built in | Fixed Point

Select the category of data to specify.

• Inherit — Inheritance rules for data types. Selecting Inherit enables a second menu/text box to the right where you can select the inheritance mode.

• Built in — Built-in data types. Selecting Built in enables a second menu/text box to the right where you can select a built-in data type.

• Fixed point — Fixed-point data types. Selecting Fixed point enables additional parameters that you can use to specify a fixed-point data type.

• Expression — Expressions that evaluate to data types. Selecting Expression enables a second menu/text box to the right, where you can enter the expression.

For more information, see Specify Data Types Using Data Type Assistant.

Dependencies

To enable this parameter, click the Show data type assistant button.

Data type override — Specify data type override mode for this signal

Inherit | Off

Select the data type override mode for this signal.

• When you select Inherit, Simulink inherits the data type override setting from its context, that is, from the block, Simulink.Signal object or Stateflow^® chart in Simulink that is using the signal.

• When you select Off, Simulink ignores the data type override setting of its context and uses the fixed-point data type specified for the signal.

For more information, see Specify Data Types Using Data Type Assistant in the Simulink documentation.

Dependencies

To enable this parameter, set Mode to Built in or Fixed point.

Tips

The ability to turn off data type override for an individual data type provides greater control over the data types in your model when you apply data type override. For example, you can use this option to ensure that data types meet the requirements of downstream blocks regardless of the data type override setting.

Signedness — Specify signed or unsigned

Signed (default) | Unsigned

Specify whether the fixed-point data is signed or unsigned. Signed data can represent positive and negative values, but unsigned data represents positive values only.

• Signed, specifies the fixed-point data as signed.

• Unsigned, specifies the fixed-point data as unsigned.

For more information, see Specify Data Types Using Data Type Assistant.

Dependencies

To enable this parameter, set the Mode to Fixed point.

Scaling — Method for scaling fixed-point data

Best precision (default) | Binary point | Slope and bias

Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Mode to Fixed point.

Word length — Bit size of the word that holds the quantized integer

16 (default) | integer from 0 to 32

Specify the bit size of the word that holds the quantized integer. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Mode to Fixed point.

Fraction length — Specify fraction length for fixed-point data type

0 (default) | scalar integer

Specify fraction length for fixed-point data type as a positive or negative integer. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Scaling to Binary point.

Slope — Specify slope for the fixed-point data type

2^0 (default) | positive, real-valued scalar

Specify slope for the fixed-point data type. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Scaling to Slope and bias.

Bias — Specify bias for the fixed-point data type

0 (default) | real-valued scalar

Specify bias for the fixed-point data type as any real number. For more information, see Specifying a Fixed-Point Data Type.

Dependencies

To enable this parameter, set Scaling to Slope and bias.

Block Characteristics

Data Types	Boolean | double | enumerated | fixed point | half | integer | single
Direct Feedthrough	yes
Multidimensional Signals	yes
Variable-Size Signals	yes
Zero-Crossing Detection	no

More About

Model Coverage

If you have a Simulink Coverage™ license and you select the Saturation on integer overflow (Simulink Coverage) parameter, the Data Type Conversion block receives saturation on integer overflow coverage. For more information, see Saturate on Integer Overflow Coverage (Simulink Coverage).

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has one default HDL architecture.

HDL Block Properties

General
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 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
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 0. For more details, see InputPipeline (HDL Coder).
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 0. For more details, see OutputPipeline (HDL Coder).

Note

With the HDL Code Advisor, you can replace Data Type Conversion blocks that use the Stored Integer (SI) mode and convert between floating-point and fixed-point data types with Float Typecast blocks.

Native Floating Point
LatencyStrategy	Specify whether to map the blocks in your design to inherit, Max, Min, Zero, or Custom for the floating-point operator. The default is inherit. See also LatencyStrategy (HDL Coder).
NFPCustomLatency	To specify a value, set LatencyStrategy to Custom. HDL Coder adds latency equal to the value that you specify for the NFPCustomLatency setting. See also NFPCustomLatency (HDL Coder).

Enumeration Data Support

This block supports code generation for enumerated signals. Use this block to cast a signal of an enumerated type to any integer type or to cast a signal of any integer type to an enumerated type.

Complex Data Support

This block supports code generation for complex signals.

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