2.2.12 Basic Transfer Procedure
illustrates the basic process a bootloader uses to transfer data and start program execution. This
process occurs after the bootloader determines the valid boot mode selected by the state of TRST and GPIO
pins.
The loader first compares the first value sent by the host against the 16-bit key value of 0x10AA. If the first word
matches the key value, the loader continuously fetches data until it transfers all the hex words and then starts
program execution. But, if the key does not match the key value, then the loader aborts and the CPU jumps to
the default flash entry point.
Read first word (W1)
W1=
0x10AA
?
No
16-bit data size
Yes
Read EntryPoint address
Read second word
(W2) and discard
upper 8-bits
?
0x08AA
W2:W1=
Yes
No
8-bit
DataSize
Data format error
Return flash
entry point
Read BlockSize (R)
?
R=0
No
Yes
Return
EntryPoint
Read BlockAddress
Transfer R words of
data from source to
destination
8-bit and 16-bit transfers are not valid for all boot modes. If only one mode is valid, then this decision tree is skipped and the key value
is only checked for correctness. See the info specific to a particular bootloader for any limitations.
In 8-bit mode, the LSB of the 16-bit word is read first followed by the MSB.
Figure 2-7. Bootloader Basic Transfer Procedure
Boot ROM
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
217
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Summary of Contents for TMS320 2806 Series
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