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Discussion Groups | Freescale DSPs | AW: 56F826 - placing large constant data array in Program Flash

Technical discussions about Freescale (Motorola) DSPs (including the DSP56000, DSP56300, DSP56600, 56800 DSPs).


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AW: 56F826 - placing large constant data array in Program Flash - Bende Georg - Jun 10 6:42:00 2003

First, you need to edit the linker_flash.cmd file, in order to create a section
in the pflash memory.
I do it like this: (56f803)
.pflash (RX) : ORIGIN = 0x0000, LENGTH = 0x6D00 # program flash memory
.pConst (RWX) : ORIGIN = 0x6D00, LENGTH = 0x1100 # constant fields

(the original was
.pflash (RX) : ORIGIN = 0x0000, LENGTH = 0x7E00 # program flash memory

If you select "Write constant data to .rodata section" in the CW5/FLASH settings
- Code Generation - M56800 Processor, then your constants will be placed
automatically in a section called ".rodata". Your fields need to be defined as
You have to place your .rodata section in the above created pConst section:

* (.rodata)
} > .pConst

Now you only need to gain access to your data, which cannot be done directly
from C. U need a snippet of assembly code:

UWord16 asm read_p_memory (int * addr)
move p:(r2)+,y0

And then you will be able to access the data like
read_p_memory((int*)&int_field[index]); Best wishes,

Georg Bende
Abteilung Elektronik
Dr. Fritz Faulhaber GmbH & Co KG
Daimlerstr. 23
71101 Schönaich
Tel: +49 7031 638294

> -----Ursprüngliche Nachricht-----
> Von: bmbmz123 [mailto:]
> Gesendet: Montag, 9. Juni 2003 16:37
> An:
> Betreff: [motoroladsp] 56F826 - placing large constant data array in
> Program Flash
> Hello all,
> I am using large constant data array tables.
> The const data extends beyond the 2k flash available in the data
> section.
> It may even extend beyond the 4k RAM available.
> I want to place the arrays in Program Flash, and read the data during
> runtime.
> An access using array-index is prferrable.
> Any suggestion?
> 10x
> bz >
> _____________________________________
> /groups.php3