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I'm trying to do the exact same thing, but just summing from 0x3FE000 to 0x3FFFBB (up to the checksum).

I cannot get the checksum to match the one in ROM.

The value I get summing the range above is 0x0000,0000,0DC6,8AD1

The 64bit checksum value in ROM for the 28031 Rev 0 part that I am using is 0x0000,093D,455C,FE90 .

The strange thing is, the one in ROM is bigger the maximum possible value; =0x2000 locations * 0xFFFF = 0x1FFF,E000.

C code snippet for the test I am doing:

#define ROM_CKSM ((const unsigned long long *)(0x3FFFBC)) /*first checksum loc, long,long=bf,be,bd,bc*/
#define ROM_BOT   ((const unsigned int *)(0x3FE000)) /*smaller number */

unsigned int *temp_uint_pntr;

unsigned long long BootROMChecksum,BootROMChecksum_expected;

temp_uint_pntr=(unsigned int *)ROM_BOT;

BootROMChecksum=0LL;

BootROMChecksum_expected=*ROM_CKSM; /* reads as: 0x0000,093D,455C,FE90 same for reading mem location ; this is not possible 8192*65535 = 0x1FFF,E000*/

while(temp_uint_pntr<(unsigned int *)ROM_CKSM) { BootROMChecksum+=(unsigned long long)*temp_uint_pntr++;  } 

if(BootROMChecksum!=*ROM_CKSM) /* 0x000000000DC6,8AD1 */
{ /* do something */

}

Great. Thanks for the quick response.

Best Regards

Anders

Did you get it to work?

I have not had any success yet using this code. 

There might be something missing in my code since I do not have checksum.h.

I made the following assumptions;

ui16 = unsigned int

ui32 = unsigned long

Also, this line confuses me:

checksum.lowHalfLSW += *currentVal ^ ((unsigned long)currentVal & 0x0000FFFF);

Should there be a * in the ((unsigned long)currentVal & 0x0000FFFF above , or are we using the address of the pointer in the checksum??

Jason,

you don't need checksum.h except for ui16 and ui32, below are the typedefs.

typedef int              i16;
typedef long             i32;
typedef unsigned int      ui16;
typedef unsigned long     ui32;

jason wiseman

ui16 = unsigned int

ui32 = unsigned long

yes, we include lower 16 bits of address in the checksum. currentVal is 32 bit variable storing the address - initialized by the line "      currentVal = memblock[i].firstAddr;"

Note that the while computing checksum we avoid the locations which store the checksum in ROM, this is done by hard initializing the memblock structure.  After computing the checksum it is compared against the checksum result stored in ROM itself.

Let us know if you have any questions. All the information needed is included within the file itself though.

Best Regards

Santosh

Yes the code works. I have replaced the ui types with Uint16, Uint32 etc which are used in the examples and changed main into a function that returns Uint16.

The following code computes the return value.

pword = (Uint16 *)CHECKSUM_ADDR;
if ((pword[0] == (Uint16)checksum.lowHalfLSW) &&
(pword[1] == (Uint16)checksum.lowHalfMSW) &&
(pword[2] == (Uint16)checksum.highHalfLSW) &&
(pword[3] == (Uint16)checksum.highHalfMSW))
return 1;
else
return 0;

Note that I have renamed currentVal to pword and removed lastVal which is only used in one place.

Thanks,

My only problem was the initialization of the memblock structure. I dont have a cinit in my system, so I changed memblock to a const.

Everything works great now.

I think the documentation for the bootloader needs to be changed. The actual checksum is quite a bit different than described in the document (sum all values in ROM as 64bit except the checksum itself).

regards,

Jason