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| R2012a Documentation → Simulink Fixed Point | |
Learn more about Simulink Fixed Point |
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| Contents | Index |
This folder contains tasks for configuring and setting up the model for data logging.
Validate model-wide settings and create simulation reference data for downstream tasks.
Preparation for Fixed-Point Conversion Using the Fixed-Point Advisor
Converting a Model from Floating- to Fixed-Point Using Simulation Data
Validate that model simulation settings allow signal logging and disable data type override to facilitate conversion to fixed point. Logged signals are used for analysis and comparison in later tasks.
Ensures that fixed-point data can be logged in downstream tasks.
| Conditions | Recommended Action |
|---|---|
The following Fixed-Point Tool setting is not set to the correct
value:
| Set Data type override to Use local settings |
| The model Configuration Parameters Data Import/Export > Signal logging check box is off. | Set to on |
| The fiprefDataTypeOverride property is not set to Off. | Set DataTypeOverride to Off |
Clicking Modify All configures the model for recommended simulation settings and fipref objects. A table displays the current and previous block settings.
Verify update diagram succeeds.
A model update diagram action is necessary for most down stream tasks.
| Conditions | Recommended Action |
|---|---|
| The model diagram does not update. | Fix the model. Make sure needed mat files are loaded. |
Updating a Block Diagram in the Simulink documentation
Identify blocks that do not support fixed-point data types.
Blocks that do not support fixed-point data types cannot be converted.
| Conditions | Recommended Action |
|---|---|
| Blocks that do not support fixed-point data types and cannot be converted exist in model. |
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Before inserting a replacement block, use the Preview link to view the replacement block. If necessary, update the settings on the replacement block to match the settings on the original block.
If the Fixed-Point Advisor does not recommend a corresponding fixed-point block, replace the unsupported block with a number of lower-level blocks to provide the same functionality.
The goal is to replace all blocks that do not support fixed-point data types. Using Data Type Conversion blocks to isolate blocks at this stage enables you to continue running through the conversion process. However, this will cause the Summarize data type task to fail downstream. To fix this failure, you must replace the block that does not support fixed-point data types.
The Simulink Block Data Type Support table summarizes characteristics of blocks in the Simulink and Simulink Fixed Point block libraries, including whether or not they support fixed-point data types.
Specify at least one signal of interest to log during simulation. Logged signals are used for analysis and comparison in other tasks. Suggested signals to log are model inports and outports.
The Fixed-Point Advisor uses logged signals to compare the initial data type to the fixed-point data type.
| Conditions | Recommended Action |
|---|---|
| No signals are logged. | If you are using simulation minimum and maximum values, specify at least one signal to be logged. Otherwise, ignore this warning. |
Log inports and outports of the system under conversion.
Simulate the model using the current solver settings, and create reference data to use for comparison and analysis. If necessary, you can stop the simulation by selecting the waitbar and then pressing Ctrl+C. To set Fixed-point instrumentation mode to Minimums, maximums and overflows, click the Modify All button.
Simulate the model using the current solver settings, create and archive reference signal data to use for comparison and analysis in downstream tasks.
Merges new simulation minimum and maximum results with existing simulation results in the active run. Allows you to collect complete range information from multiple test benches. Does not merge signal logging results.
| Conditions | Recommended Action |
|---|---|
| Simulation does not run. | Fix errors so simulation will run. |
| Fixed-point instrumentation mode is not set to Minimums, maximums and overflows | If you are using simulation minimum and maximum values, set Fixed-point instrumentation mode to Minimums, maximums and overflows. Otherwise, ignore this warning. |
Clicking Modify All sets Fixed-point instrumentation mode to Minimums, maximums and overflows. A table displays the current and previous block settings.
If the simulation is set up to have a long simulation time, after starting the run of this task you can stop the simulation by selecting the waitbar and then pressing Ctrl+C. This allows you to change the simulation time and continue without having to wait for the long simulation to complete.
Specifying small simulation run times reduces task processing times. You can change the simulation run time in the Configuration Parameters dialog box. See Start time and Stop time in the Simulink reference for more information.
Verify modeling guidelines related to fixed-point conversion goals.
Validate model-wide settings.
Preparation for Fixed-Point Conversion Using the Fixed-Point Advisor
Converting a Model from Floating- to Fixed-Point Using Simulation Data
Verify that model Configuration Parameters > Diagnostic > Data Validity parameters are not set to error.
If the Configuration Parameters > Diagnostic > Data Validity parameters are set to error, the model update diagram action fails in downstream tasks.
| Conditions | Recommended Action |
|---|---|
| Detect downcast is set to error. | Set all Configuration Parameters > Diagnostics > Data Validity > Parameters options to warning. |
| Detect overflow is set to error. | |
| Detect underflow is set to error. | |
| Detect precision loss is set to error. | |
| Detect loss of tunability is set to error. |
Clicking Modify All sets all Configuration Parameters > Diagnostics > Data Validity > Parameters options to warning. A table displays the current and previous settings.
Confirm that Simulink simulations are configured to treat logic signals as Boolean data.
Configuring logic signals as Boolean data optimizes the code generated in downstream tasks.
| Conditions | Recommended Action |
|---|---|
| Implement logic signals as Boolean data is set to off. | Set Configuration Parameters > Optimization > Implement logic signals as Boolean data to on. |
Clicking Modify All selects the model Configuration Parameters > Optimization > Implement logic signals as Boolean data check box. A table displays the current and previous parameter settings.
Identify any Mux block used as a bus creator and any bus signal treated as a vector.
This task identifies:
Mux blocks that are bus creators
Bus signals that the top-level model treats as vectors
| Conditions | Recommended Action |
|---|---|
| The Fixed-Point Advisor is not operating on a top-level model | If this task is important to your conversion, start the Fixed-Point Advisor on the top-level model. |
| The model is not configured to detect future changes that might result in improper bus usage. | Set Configuration Parameters > Diagnostics > Connectivity > Buses > Bus signal treated as vector to error. |
Note This task is a Simulink task. For more information, see Check for proper bus usage in the Simulink documentation. |
Verify that model Configuration Parameters > Diagnostics > Simulation range checking is not set to none.
If Configuration Parameters > Diagnostics > Simulation range checking is set to none, the simulation does not generate any range checking warnings.
| Conditions | Recommended Action |
|---|---|
| Configuration Parameters > Diagnostics > Simulation range checking is set to none. | Set Configuration Parameters > Diagnostics > Simulation range checking to warning. |
Clicking Modify All sets Configuration Parameters > Diagnostics > Simulation range checking to warning.
Check if model uses implicit signal resolution.
Models with implicit signal resolution attempt to resolve all named signals and states to Simulink signal objects, which is inefficient and slows incremental code generation and model reference. This task identifies those signals and states for which you may turn off implicit signal resolution and enforce resolution.
| Conditions | Recommended Action |
|---|---|
| Model uses implicit signal resolution. |
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Clicking Modify All sets the model Configuration Parameters > Diagnostics > Data Validity > Signal resolution to Explicit only and enforces resolution for each of the signals and states in the model. Tables display the current and previous settings.
Resolving Signal Objects for Output Data in the Simulink documentation
 | Fixed-Point Advisor | Prepare for Data Typing and Scaling |  |
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