CCS 6, TMS320C28x and absolute variable addresses

Hank Barta

Hi all,

I'm looking for options for locating variables at specific memory address (for external devices mapped via EMIF.) I'm familiar with using a pointer and assigning it the address but I'm looking for something where I can declare a variable and tell the linker where it should be. I found a page at that describes the LOCATION pragma but that seems not to work with CCS 6 and this processor. I can use the DATA_SECTION pragma and corresponding entry in the linker command file, but I'd really prefer to keep everything in one place and in the C/C++ source if possible. I've searched the compiler manual spru514j.pdf for a way to do this but was unable to find anything.

Is there a pragma or keyword that will locate a variable at an absolute address?

Thanks!

over 7 years ago

0 Hank Barta over 7 years ago

Intellectual 970 points

Not so fast on the DATA_SECTION pragma apparently. I have the following in my source:

// SDRAM mapped using CS0 starting at 0x9000 0000
#pragma SET_DATA_SECTION("_SDRAM_")
volatile int16 external_sdram[0x1000000];	// 0x9000 0000
#pragma SET_DATA_SECTION()

In the linker command file

MEMORY
{
	PAGE 0:    /* Program Memory */
   /* flash */
    APPCODE     : origin = 0x088000, length = 0x038000	   /* on-chip FLASH E..N */
	
	
	PAGE 1 :   /* Data Memory */

   RAMD0           	: origin = 0x00B000, length = 0x000800
   RAMD1           : origin = 0x00B800, length = 0x000800
	
...

/* from SPRS880G: EMIF1_CS4n - Program + Data 393K <D7> 16 0x0038 0000 0x003D FFFF Yes */
   FPGA             : origin = 0x380000, length = 0x060000			/* start of FPGA */
/* from SPRS880G: EMIF1_CS0n - Data 256M × 16 0x8000 0000 0x8FFF FFFFF Yes */
   SDRAM             : origin = 0x80000000, length = 0x10000000		/* start of SDRAM */
}

and

	_FPGA_ : align(4) > FPGA,      PAGE = 1,
   		//LOAD_END(__PARTITION_END_7)
			{
				__PARTITION_TYPE_7 = __PT_DATA + __PF_INIT;
				__PARTITION_START_7 = .;
				*(_FPGA_)
				. = align(4);
			}

	_SDRAM_ : align(4) > FPGA,      PAGE = 1,
   		//LOAD_END(__PARTITION_END_8)
			{
				__PARTITION_TYPE_8 = __PT_DATA + __PF_INIT;
				__PARTITION_START_8 = .;
				*(_SDRAM_)
				. = align(4);
			}

The FPGA section builds and links w/out difficulty but when it comes to the SDRAM section, I get the following error:

"C:/path/to/proj/BlinkLEDs/build/BlinkLEDs.cmd", line 125: error #10099-D: program will not fit into available memory.  run placement with alignment/blocking fails for section "_SDRAM_" size 0x1000000 page 1.  Available memory ranges:
   FPGA         size: 0x60000      unused: 0x57fc0      max hole: 0x57fc0   
error #10010: errors encountered during linking;

Length for SDRAM is set to 0x1000 0000 but the error reports 0x100 0000. (Spaces inserted to make counting zeroes easier. ;)

There must be something I've overlooked but I can't figure that out.

The FPGA section seems to work as expected.

Thanks!

0 Richard Poley over 7 years ago in reply to Hank Barta

TI__Mastermind 27200 points

Hank,

Shouldn't this line...

_SDRAM_ : align(4) > FPGA,      PAGE = 1,

...be...

_SDRAM_ : align(4) > SDRAM,      PAGE = 1,

...?  I think you're mapping everything into the same section.

Regards,

Richard

0 Hank Barta over 7 years ago in reply to Richard Poley

Intellectual 970 points

Yes - Thanks!

I thought I was making that kind of mistake but several minutes of staring at the code did not reveal.

thanks,
hank

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CCS 6, TMS320C28x and absolute variable addresses