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MOTLoad Firmware
MVME3100 Single Board Computer Installation and Use (6806800M28C)
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3.10 Boot Images
Valid boot images whether POST, USER, or MCG, 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:
3.10.1 Checksum Algorithm
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;
Name Type Size Notes
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 32 User defined
ImageRamAddress unsigned integer 1 RAM address
ImageOffset unsigned integer 1 Offset from header start to entry
ImageFlags unsigned integer 1 Refer to Image Flags on page 63
ImageVersion unsigned integer 1 User defined
Reserved unsigned integer 8 Reserved for expansion