Fixed-Point Blockset Release Notes

Chapter 3
Fixed-Point Blockset 3.0 Release Notes

New Features

This section introduces the new features and enhancements added in the Fixed-Point Blockset 3.0 since the Fixed-Point Blockset 2.0 (Release 11.0).

This section is organized into these subsections:

• New Blocks
• New Functions
• Data Type Support
• Data Type and Scaling Inheritance
• Increased Speed, Efficiency, and Accuracy
• Overflow Logging
• Simulink Accelerator
• Model Parameter Configuration
• Display of Scaling Information

New Blocks

The Fixed-Point Blockset 3.0 includes the new blocks listed below.

Block Name	Description
Abs	Output the absolute value of the input.
Bitwise Operator	Perform the specified bitwise operation on the inputs.
Data Type Propagation	Configure the data type and scaling of the propagated signal based on information from the reference signals.
Dead Zone	Provide a region of zero output.
Dot Product	Generate the dot product.
Gateway In Inherited	Convert a Simulink data type to a Fixed-Point Blockset data type, and inherit the data type and scaling.
Integer Delay	Delay a signal N sample periods.
Look-Up Table Dynamic	Approximate a one-dimensional function using a selected look-up method and a dynamically specified table.
MinMax	Output the minimum or maximum input value.
Multiport Switch	Switch output between different inputs based on the value of the first input.
Sign	Indicate the sign of the input.
Tapped Delay	Delay a scalar signal multiple sample periods, and output all the delayed versions.
Unary Minus	Negate the input.

New Functions

The Fixed-Point Blockset 3.0 includes the new functions listed below.

Function Name	Description
fixptbestexp	Determine the exponent that gives the best precision fixed-point representation of a value.
fixptbestprec	Determine the maximum precision available for the fixed-point representation of a value.
fixpt_convert	Convert Simulink models and subsystems to fixed-point equivalents.
fixpt_convert_prep	Prepare a Simulink model for more complete conversion to fixed point.
fixpt_restore_links	Restore links for fixed-point blocks.

Data Type Support

The Fixed-Point Blockset 3.0 has expanded its data type support:

• You can connect Simulink blocks directly to Fixed-Point Blockset blocks provided the signals use built-in Simulink data types. However, a fixed-point signal consisting of 8-, 16-, or 32-bit integers is compatible with Simulink only when its scaling is given by a slope of 1 and a bias of 0.
• Many important Simulink blocks have added support for fixed-point signals. Key blocks include Enable, Trigger, Scope, Display, and To Workspace.
• Fixed-point blocks now support complex numbers.

Data Type and Scaling Inheritance

Many fixed-point blocks support the inheritance of data type and scaling information from other blocks. The two possible inheritance options are:

• Inherit via internal rule--The output data type and scaling are inherited from the block input(s). The goal of the inheritance rule is to select the "natural" data type and scaling for the output. The specific rule that is used depends on the block operation. For example, if you are multiplying two signed 16-bit signals, the Product block produces the natural output of a signed 32-bit data type.
• Inherit via back propagation--The output data type and scaling are inherited by back propagation. In many cases, you will use the Data Type Propagation block with this option.

Increased Speed, Efficiency, and Accuracy

• Simulation speed has been increased by approximately 2.5 times.
• On average, fixed-point signals use 20 times less memory.
• Interpolation is more accurate and the number of quantization steps has been reduced.
• Generated code is significantly simpler.
• Unsigned numbers avoid overflow in these situations:
• Interpolation when the slope of the output data is negative
• Conversion when the bias adjustment is negative
• Addition and subtraction when the bias adjustment is negative

Overflow Logging

Indirect logging of overflows and saturations via percent range error has been replaced by explicit logging.

Simulink Accelerator

You can now use the Simulink Accelerator in conjunction with the Fixed-Point Blockset. However, you cannot log minimum and maximum simulation values or overflows.

Model Parameter Configuration

You can now use the Model Parameter Configuration dialog box to override the Inline parameters option for selected parameters. You access this feature by selecting the Configure button on the Advanced tab of the Simulation Parameters dialog box. Previously, code generation for fixed point blocks required all parameters to be inline, or all parameters to be tunable.

Display of Scaling Information

To significantly improve simulation speed, the scaling information associated with fixed-point blocks is no longer updated. Since this scaling information can become obsolete, you should remove it by running fixpt_clear_tag or slupdate. To view data type and scaling information, you should select Port data types under the model's Format menu.

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