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| R2011b Documentation → Simulink Fixed Point | |
Learn more about Simulink Fixed Point |
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| Contents | Index |
Configure blocks with data type inheritance or constraints to avoid data type propagation errors.
The block settings from this folder simplifies the initial scaling. The optimal block configuration is achieved in later stages. The tasks in this folder are preparation for scaling, not actual scaling.
Block output and parameter minimum and maximum values can be specified in this step.
Review blocks that currently have their scaling locked down and will be excluded from autoscaling.
When blocks have their scaling locked, the Fixed-Point Advisor excludes them from autoscaling. This task identifies blocks that have locked scaling so that you can unlock them.
| Conditions | Recommended Action |
|---|---|
| Blocks have locked scaling. | Unlock scaling on blocks that currently have locked scaling. |
Clicking Modify All unlocks scaling on blocks that currently have locked scaling.
Identify blocks with an inherited output signal data type.
Inherited data types might lead to data type propagation errors.
For floating-point inheritance blocks with floating-point inputs or outputs, the Fixed-Point Advisor replaces the inheritance with the fixed-point data type specified by the user. For floating-point inheritance blocks with fixed-point output and other Simulink and DSP System Toolbox and Communications System Toolbox™ blocks, the Fixed-Point Advisor now detects inheritance and replaces it with the compiled data type.
What are Floating-Point Inheritance Blocks?
Enter a default fixed-point data type to use for floating-point inheritance blocks, or select one from the list:
| undefined |
| int8 |
| uint8 |
| int16 |
| uint16 |
| int32 |
| uint32 |
| fixdt(1,16,4) |
| Conditions | Recommended Action |
|---|---|
| An input parameter is invalid. | Enter or select a valid value for the Data type for blocks with floating-point inheritance input parameter. |
| The system or subsystems contain floating-point inheritance blocks that have floating-point inputs. | Set the block output data type to the recommended data type. Remove floating-point inheritance for these blocks by explicitly configuring the Output data type or Output data type mode parameter to the recommended value where possible. |
| Blocks or Stateflow output data in the current system or subsystems have inherited output data types. | Remove output data type inheritance for blocks by explicitly configuring the Output data type or Output data type mode parameter to the recommended value where possible. |
| Remove output data type inheritance for Logical Operator blocks by clearing the Require all inputs and outputs to have the same data type parameter parameter. | |
| Remove Stateflow output data type inheritance by explicitly configuring the output data Type property. |
Clicking Modify All explicitly configures the output data types to the recommended values where possible. Tables list the previous and current data types for the reconfigured blocks.
Identify blocks with input data type constraints.
Blocks that have input data type constraints might lead to data type propagation errors.
| Conditions | Recommended Action |
|---|---|
| The input data types of blocks or Stateflow charts in the current system or subsystems have constraints. | Explicitly configure flexible input data types for blocks by setting the InputSameDT parameter to off where possible. |
| Explicitly configure Logical Operator blocks to have flexible input data types by setting the AllPortsSameDT parameter to off. | |
| Explicitly configure flexible Stateflow chart input data types by setting the Type method to Inherited. | |
| Select the Use Strong Data Typing with Simulink I/O chart property. |
Clicking Modify All explicitly configures the specified settings to the recommended value where possible. A table lists the previous and current settings for the reconfigured blocks.
Removing unnecessary data setting restrictions makes it more likely that the Propose data types task will succeed downstream.
Verify all Stateflow charts are configured to have strong data typing with Simulink I/O.
Identify mismatches between input or output fixed-point data in Stateflow charts and their counterparts in Simulink models.
| Conditions | Recommended Action |
|---|---|
| Stateflow charts do not have strong data typing with Simulink I/O. | Select the Use Strong Data Typing with Simulink I/O check box in the chart properties dialog. |
Clicking Modify All configures all Stateflow charts to have strong data typing with Simulink I/O.
Identify and remove redundant data type specification originating from blocks and Simulink signal objects.
This task prepares your model for scaling by identifying and removing redundant data type specification originating from blocks and Simulink signal objects.
Note You must rerun this task whenever you delete or manipulate a Simulink signal object in the base workspace. This task is preparation for scaling. |
Select from the list:
| Blocks Identify and remove redundant data type specification from blocks. |
| Signal objects Identify and remove redundant data type specification from Simulink signal objects. |
| Conditions | Recommended Action |
|---|---|
| Blocks associated with Simulink signal objects do not have their data type specification set to a passive mode. | Set the data type specification of these blocks to a passive mode, such as Inherit via back propagation. |
| Simulink signal objects associated with blocks do not have their data type specification set to a passive mode. | Set the data type specification of these Simulink signal objects to Auto. |
Clicking Modify All explicitly configures the properties of the blocks or Simulink signal objects to the recommended value where possible. A table displays the current and previous settings.
Verify target hardware setting.
Review the hardware device settings and verify they are the settings you intend to use.
Enter a default fixed-point data type to use for all floating-point signals, or select one from the list. For FPGA/ASIC targets, specify the type explicitly.
| Remain floating-point Use this setting if you are converting only part of the model to fixed point and want to leave the rest of the model as floating point. |
| Same as embedded hardware integer Use this setting if the hardware device specified is a microprocessor. |
| int8 |
| int16 |
| int32 |
| fixdt(1,16,4) |
| Conditions | Recommended Action |
|---|---|
| The model's Configuration Parameters > Hardware Implementation device parameters are not specified. | Provide values for the Configuration Parameters > Hardware Implementation > Device vendor and Device type parameters. |
| Default data type of all floating-point signals is set to Remain floating-point | For microprocessors, set to Same as embedded hardware integer. For FPGA/ASIC, set the data type explicitly. The Fixed-Point Advisor uses the sign and word length of this data type. |
Specify block output and parameter minimum and maximum values.
Block output and parameter minimum and maximum values are used for fixed-point scaling in other tasks. Typically, they are determined during the design process based on the system you are creating.
| Conditions | Recommended Action |
|---|---|
| Minimum and maximum values are not specified for Inport blocks. | Specify minimum and maximum values for Inport blocks. |
| Warning if no simulation minimum or maximum for any signals. | If you are using simulation minimum and maximum data, return to "Create simulation reference data" to set up signal logging. |
In this task, you can specify minimum and maximum values for any block.
You can promote simulation minimum and maximum values to output minimum and maximum values using the Model Advisor Result Explorer, launched by clicking the Explore Result button. In the center pane of the Model Advisor Result Explorer, use the check boxes in the PromoteSimMinMax column to promote values.
If you do not specify block minimum and maximum values, the Propose data types task might fail later in the conversion.
Batch-Fixing Warnings or Failures in the Simulink documentation.
 | Prepare Model for Conversion | Return to the Fixed-Point Tool to Perform Data Typing and Scaling |  |
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