Texas Instruments TMS320 DSP Design-Time Object Creation, Run-Time Object Creation and Deletion

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Interfaces and Modules

Figure 3-2. Module Object Creation

FIR

FIR_Config FIR;

FIR_init();

FIR_exit();

FIR_create();

Creates

firObject

firObject

Figure 3-3illustrates an object appropriate for a finite impulse response filter implemented by a module named FIR.

Figure 3-3. Example Module Object

FIR Creates

FIR_create();

firObject

Int length;

Int coeff[];

Int delay[];

Read-only coefficient array

Filter input history buffer

3.1.5 Design-Time Object Creation

Many embedded systems are very static in nature; memory, MIPS, and I/O peripherals are statically partitioned among a fixed set of functions that operate continuously until power is removed. Static systems admit a number of performance optimizations that simply are not possible in dynamic systems. For example, there is no need for a memory manager in a static system and general data structures, such as linked lists, can be often replaced with much simpler and more efficient structures, such as fixed length arrays. These optimizations not only reduce the system'sCode size requirements; they may also have a significant effect on the execution performance of the system.

When designing a system that is very cost sensitive, must operate with limited power, or has limited MIPS, designers look for portions of the system that can be fixed at design time (i.e., made static). Even if the entire system cannot be static, often certain sub-systems can be fixed at design time. It is important, therefore, that all modules efficiently support static system designs.

Guideline 3

All modules that support object creation should support design-time object creation.

In practice, this simply means that all functions that are only required for run-time object creation be placed either in separate compilation units or separate COFF output sections that can be manipulated by the linker. Ideally, every function should be in a separate compilation unit. This allows the system integrator to eliminate run-time support that is unnecessary for a static system.

3.1.6 Run-Time Object Creation and Deletion

Modules may optionally support run-time object creation and deletion. In some applications, run-time creation and deletion is a requirement. For example, without the ability to remove unneeded objects and reuse memory, the physical constraints of the system make it impossible to create rich multi-function applications.

Run-time creation of objects is valuable even in systems that do not support or require run-time deletion of these objects. The precise nature of the objects, the number of objects, and even the type of objects created may be a function of parameters that are only available at run-time. For example, you may want to create a single program that works in a variety of hardware platforms that differ in the amount of memory available and this amount is determinable at run-time.

SPRU352G –June 2005 –Revised February 2007 Algorithm Component Model 29

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