Motorola MVME3100 User Manual

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MVME3100>

Valid boot images whether POST, USER, or Alternate MOTLoad, are located on 1MB 
boundaries within flash. The image may exceed 1MB in size. An image is determined valid 
through the presence of two "valid image keys" and other sanity checks. A valid boot image 
begins with a structure as defined in the following table:

The checksum algorithm is a simple unsigned word add of each word (4 byte) location in the 
image. The image must be a multiple of 4 bytes in length (word-aligned). The content of the 
checksum location in the header is not part of the checksum calculation. The calculation 
assumes the location to be zero. The algorithm is implemented using the following code:

Unsigned int checksum(

Unsigned int *startPtr,/* starting address */

Unsigned int endPtr/* ending address */

) {

unsigned int checksum=0;

while (startPtr < endPtr) {

checksum += *startPtr;

startPtr++;

}

return(checksum);

}

UserDefined

unsigned integer

8

User defined

ImageKey 1

unsigned integer

1

0x414c5420

ImageKey 2

unsigned integer

1

0x424f4f54

ImageChecksum

unsigned integer

1

Image checksum

ImageSize

unsigned integer

1

Must be a multiple of 4

ImageName

unsigned character

20

User defined

ImageRamAddress

unsigned integer

1

RAM address

ImageOffset

unsigned integer

1

Offset from header start to entry

ImageFlags

unsigned integer

1

Refer to 

ImageVersion

unsigned integer

1

User defined

Reserved

unsigned integer

8

Reserved for expansion