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Checksum Algorithm
Name
ImageOffset
ImageFlags
ImageVersion
Reserved
6.7.1
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;
startPtr++;
}
return(checksum);
}
6.7.2
Image Flags
The image flags of the header define various bit options that control how the image will be
executed.
Table 6-2 MOTLoad Image Flags
Name
COPY_TO_RAM
IMAGE_MCG
IMAGE_POST
DONT_AUTO_RUN
COPY_TO_RAM
If set, this flag indicates that the image is to be copied to RAM at the address specified in
the header before control is passed. If not set, the image will be executed in flash. In both
instances, control will be passed at the image offset specified in the header from the base
of the image.
IMAGE_MCG
If set, this flag defines the image as being an Alternate MOTLoad, as opposed to USER,
image. This bit should not be set by developers of alternate boot images.
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Type
Size
unsigned integer
1
unsigned integer
1
unsigned integer
1
unsigned integer
8
Value
Interpretation
0x00000001
Copy image to RAM at ImageRamAddress before execution
0x00000002
Alternate MOTLoad image
0x00000004
POST image
0x00000008
Image not to be executed
MOTLoad Firmware
Notes
Offset from header start to entry
Refer to
Image Flags on page 95
User defined
Reserved for expansion
95
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