DSP Implementation Lecture 3

1. DSP Implementation Lecture 3

2. Anatomy of a DSP Project In VDSP • Linker Description File (.LDF) • Source Files (.asm,.c,.h,.cpp,.dat) • Object Files (.doj) • Library Files (.dlb) • Project File (.dpj)

3. Linker Description File • Provides link between hardware memory map and C/C++ Model • Basic Sections – Required by C model.

4. Section seg_pmco This section must be in Program Memory, holds code, and is required by some functions in the C/C++ run-time library. The Program Memory code section, seg_pmco, is where the compiler puts all the program instructions that it generates when you compile your program. When linking, use your linker description file to map this section to Program Memory space.

5. Section seg_dmda The Data Memory data section, seg_dmda, is where the compiler puts global and static data in Data Memory. When linking, use your linker description file to map this section to Data Memory space. By default, the compiler stores static variables in the Data Memory data section. The compiler’s dm and pm keywords (memory type qualifiers) let you override this default. If a memory type qualifier is not specified, the compiler places static and global variables in Data Memory. The following example allocates an array of 10 integers in the Data Memory data section: static int data [10];

6. Section seg_pmda The Program Memory data section, seg_pmda, is where the compiler puts global and static data in Program Memory. When linking, use your linker description file to map this section to Program Memory space. By default, the compiler stores static variables in the Data Memory data section. The compiler's pm keyword (memory type qualifier) lets you override this default and place variables in the Program Memory data section. If a memory type qualifier is not specified, the compiler places static and global variables in Data Memory. The following example allocates an array of 10 integers in the Program Memory data section: static int pm coeffs[10];

7. Section seg_stak The run-time stack section, seg_stak, is where the compiler puts the run-time stack in Data Memory. When linking, use your linker description file to map this section to Data Memory space. Because the run-time environment cannot function without this section, you must define it, and the section must be in Data Memory space. A typical size for the run-time stack is 4K 32-bit words of Data Memory. The run-time stack is a 32-bit wide structure, growing from high memory to low memory. The compiler uses the run-time stack as the storage area for local variables and return addresses. During a function call, the calling function pushes the return address onto the stack.

8. Section seg_heap The run-time heap section, seg_heap, is where the compiler puts the run-time heap in Data Memory. When linking, use your Linker Description File (.ldf) to map the seg_heap section to Data Memory space. A typical size for the run-time heap is 60K 32-bit words of Data Memory. To dynamically allocate and deallocate memory at run-time, the C or C++ run-time library includes five functions: malloc, calloc, realloc and free. These functions allocate memory from the seg_heap section of memory by default.

9. Section seg_init The initialization section, seg_init, is where the compiler puts the initialization data in Program Memory. When linking, use your linker description file to map this section to Program Memory space.

10. Section seg_rth The run-time header section, seg_rth, is where the compiler puts the system initialization code and interrupt table in Program Memory. When linking, use your linker description file to map this section to the interrupt vector table area of Program Memory space. 161_hdr.doj or 161_cpp_hdr.doj