| Embedded Target for Texas Instruments C6000 DSPs | |
Cautions Regarding Writing Directly to Memory
When you write filter coefficients directly to target memory, you need to allocate sufficient memory for the coefficients, and proceed with caution when you update your filter coefficients in target memory.
Allocating Sufficient or Extra Memory for Filter Coefficients
When you export filter coefficients directly to target memory, the filter coefficients overwrite as many memory locations as they need. The export process does not check whether you allocated sufficient memory for your filter coefficients. You must allocate enough memory for your filter coefficients or you may get unexpected results. To ensure you allocate enough target memory for your filter, export the filter by generating a C header file, as described in Tutorial--Exporting Filters from FDATool to CCS IDE.
You can allocate extra memory by editing the generated C header file, and then loading the associated program file into your target as described in the tutorial in Step 8--Export the Filter by Generating a Program File. Allocating extra memory provides more freedom for changing a filter and overwriting its previous version stored in target memory. Even after you allocate extra memory, you should still proceed with caution when overwriting old filter coefficients with updated coefficients as discussed in the next section.
Overwriting Old Filter Coefficients with Updated Coefficients
When you tune a filter to overwrite its previous version in target memory, carefully consider changes that increase the memory required to store the filter coefficients, or that alter the export data type.
Do Not Tune a Filter's Export Data Type. Never tune a filter by changing its data type, because the allocated memory expects the data type of the first version of the filter that you exported. Overwriting a filter with a filter that has a different data type usually yields unexpected results.
Be Wary of Filter Changes that Increase Memory Required to Store Filter Coefficients. If you do not allocate extra memory when exporting the first version of your filter, do not tune the filter in ways that increase the memory required to store its coefficients. For instance, you should not increase the order of the filter. When you overwrite your original filter with one of a higher order, the updated filter may overwrite data in memory locations that you did not intend for storing filter coefficients. Even if you do allocate extra memory for your filter coefficients, be cautious about making changes that increase the memory required to store the coefficients. Examples of such changes include
| | Selecting the Export Mode | Variables and Memory Necessary for Filter Export | |