Data Type Conversion - Convert input signal to specified data type

Library

Signal Attributes

Description

The Data Type Conversion block converts an input signal of any Simulink software data type to the data type and scaling you specify for the Output data type parameter. 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.

Note   This block requires that you specify the data type and/or scaling for the conversion. If you want to inherit this information from an input signal, you should use the Data Type Conversion Inherited block.

The Input and output to have equal parameter controls how the input is processed. The possible values are Real World Value (RWV) and Stored Integer (SI):

• Select Real World Value (RWV) to treat the input as V = SQ + B where S is the slope and B is the bias. V is used to produce Q = (V - B)/S, which is stored in the output. This is the default value.

• Select Stored Integer (SI) to treat the input as a stored integer, Q. The value of Q is directly used to produce the output. In this mode, the input and output are identical except that the input is a raw integer lacking proper scaling information. Selecting Stored Integer may be useful in these circumstances:

  • If you are generating code for a fixed-point processor, the resulting code only uses integers and does not use floating-point operations.

  • If you want to partition your model based on hardware characteristics. For example, part of your model may involve simulating hardware that produces integers as output.

Working with Fixed-Point Values Greater than 32 Bits

The MATLAB built-in integer data types are limited to 32 bits. If you want to output fixed-point numbers that range between 33 and 53 bits without loss of precision or range, you should break the number into pieces using the Gain block, and then output the pieces using the Data Type Conversion block to store the value inside a double.

Suppose that the original signal is an unsigned 128-bit value with default scaling. You can break this signal into four pieces using four parallel Gain blocks configured with the gain and output settings shown below.

For each Gain block, you must also configure the Integer rounding mode parameter to Floor and clear the Saturate on integer overflow check box.

Working with Enumerated Signals

You can use a Data Type Conversion block to cast signal of an enumerated type to a signal of any numeric type, provided that the underlying integers of all enumerated values input to the block are within the range of the numeric type. Otherwise, an error occurs during simulation.

You can use a Data Type Conversion block to cast a signal of any integer type to a signal of an enumerated type, provided that every value input to the Data Type Conversion block is the underlying integer of some value in the enumerated type. Otherwise, an error occurs during simulation.

You cannot use a Data Type Conversion block to cast a non-integer numeric signal an enumerated signal. You cannot cast a complex signal to an enumerated signal regardless of the data types of its real and imaginary parts. See Using Enumerated Data for information about enumerated data types in Simulink.

When you generate code for a Data Type Conversion block that casts to an enumerated type, the code uses safe casting if the block's Saturate on integer overflow option is selected. If the option is cleared, the code does not use safe casting to enumerated types. See Enumerated Type Safe Casting for more information.

Data Type Support

The Data Type Conversion block handles any data type supported by Simulink software, including fixed-point and enumerated data types.

For a discussion on the data types supported by Simulink software, see Data Types Supported by Simulink.

Parameters and Dialog Box

Show data type assistant

Display the Data Type Assistant.

Settings

The Data Type Assistant helps you set the Output data type parameter.

See Specifying Block Output Data Types for more information.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Lock output data type setting against changes by the fixed-point tools

Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor.

Settings

Default: Off

On

Locks the output data type setting for this block.

Off

Allows the Fixed-Point Tool and the Fixed-Point Advisor to change the output data type setting for this block.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

For more information, see Fixed-Point Tool and Fixed-Point Advisor in the Simulink Fixed Point documentation.

Input and output to have equal

Specify which type of input and output should be equal.

Settings

Default: Real World Value (RWV)

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.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Integer rounding mode

Select the rounding mode for fixed-point operations.

Settings

Default: Floor

Ceiling

Round both positive and negative numbers toward positive infinity.

Convergent

Round number to the nearest representable value. If a tie occurs, round to the nearest even stored value.

Floor

Round both positive and negative numbers toward negative infinity.

Nearest

Round number to the nearest representable value. If a tie occurs, round toward positive infinity.

Round

Round number to the nearest representable value. If a tie occurs, round positive numbers toward positive infinity and round negative numbers toward negative infinity.

Simplest

This option provides for an optimization of the rounding code for several blocks.

Zero

Round number toward zero.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

For more information, see Rounding in the Simulink Fixed Point User's Guide.

Saturate on integer overflow

Specify whether overflows saturate.

Settings

Default: Off

On

Overflows saturate.

Off

Overflows do not saturate.

Tips

• 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 which case, no saturation code is necessary.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Sample time (-1 for inherited)

Enter the discrete interval between sample time hits or specify another appropriate sample time such as continuous or inherited.

Settings

Default: -1

By default, the block inherits its sample time based upon the context of the block within the model. To set a different sample time, enter a valid sample time based upon the table in Types of Sample Time.

See also How to Specify the Sample Time in the online documentation for more information.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Output minimum

Specify the minimum value that the block should output.

Settings

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

Tip

This number must be a double scalar value.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Output maximum

Specify the maximum value that the block should output.

Settings

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

Tip

This number must be a double scalar value.

Command-Line Information

See Block-Specific Parameters for the command-line information.

Output data type

Specify the output data type.

Settings

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)

Inherit: Inherit via internal rule

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.

Inherit: Inherit from 'Constant value'

Use data type of Constant value parameter. This option appears for some blocks.

Inherit: Inherit via back propagation

Use data type of the driving block.

Inherit: Same as input

Use data type of sole input signal. This option appears for some blocks.

Inherit: Same as first input

Use data type of first input signal. This option appears for some blocks.

Inherit: Same as accumulator

Output data type is the same as accumulator data type. This option appears for some blocks.

double

Output data type is double.

single

Output data type is single.

int8

Output data type is int8.

uint8

Output data type is uint8.

int16

Output data type is int16.

uint16

Output data type is uint16.

int32

Output data type is int32.

uint32

Output data type is unt32.

fixdt(1,16,0)

Output data type is fixed point fixdt(1,16,0).

fixdt(1,16,2^0,0)

Output data type is fixed point fixdt(1,16,2^0,0).

Enum: <class name>

Use an enumerated data type, for example, Enum: BasicColors. This option appears for some blocks.

<data type expression>

Use a data type object, for example, Simulink.NumericType.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying Block Output Data Types in the Simulink User's Guide for more information.

Mode

Select the category of data to specify.

Settings

Default: Inherit (Constant, Data Type Conversion, Discrete Time Integrator, Gain, Inport, Outport, Product, Saturation, Sum, Switch), Built in (Logical Operator, Relational Operator)

Inherit

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

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

Fixed-point data types.

Enumerated

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>

Expression

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>

Dependency

Clicking the Show data type assistant button enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Using the Data Type Assistant in the Simulink User's Guide.

Signedness

Specify whether you want the fixed-point data as signed or unsigned.

Settings

Default: Signed

Signed

Specify the fixed-point data as signed.

Unsigned

Specify the fixed-point data as unsigned.

Dependencies

Selecting Mode > Fixed point enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.

Word length

Specify the bit size of the word that holds the quantized integer.

Settings

Default: 16

Minimum: 0

Maximum: 32

Large word sizes represent large values with greater precision than small word sizes.

Dependencies

Selecting Mode > Fixed point enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.

Scaling

Specify the method for scaling your fixed-point data to avoid overflow conditions and minimize quantization errors.

Settings

Default: Best precision (Constant), Binary point (Data Type Conversion, Discrete-Time Integrator, Gain, Inport, Outport, Product, Saturation, Sum, Switch), Integer (Logical Operator, Relational Operator)

Binary point

Specify binary point location.

Slope and bias

Enter slope and bias.

Best precision

Specify best-precision values. This option appears for some blocks.

Integer

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.

Dependencies

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

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.

Fraction length

Specify fraction length for fixed-point data type.

Settings

Default: 0

Binary points can be positive or negative integers.

Dependencies

Selecting Scaling > Binary point enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.

Slope

Specify slope for the fixed-point data type.

Settings

Default: 2^0

Specify any positive real number.

Dependencies

Selecting Scaling > Slope and bias enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.

Bias

Specify bias for the fixed-point data type.

Settings

Default: 0

Specify any real number.

Dependencies

Selecting Scaling > Slope and bias enables this parameter.

Command-Line Information

See Block-Specific Parameters for the command-line information.

See Also

See Specifying a Fixed-Point Data Type in the Simulink User's Guide for more information.

/* Sum Block: <Root>/Sum
   *
   *  y =  u0 + u1
   *
   * Input0  Data Type:  Fixed Point    S16  2^-2
   * Input1  Data Type:  Fixed Point    S16  2^-4
   * Output0 Data Type:  Fixed Point    S16  2^-5
   *
   * Round Mode: Floor
   * Saturation Mode: Wrap
   *
   */
  sum = ((in1) << 3);
  sum += ((in2) << 1);

Characteristics

See Also

Data Type Conversion Inherited

Data Store Write

Data Type Conversion Inherited

Related Products & Applications

• Simulink
• Control Design
• Signal Processing & Communications
• Model-Based Design
• Physical Modeling
• Verification & Validation

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