可以啊，写的很明白啊。
The Boot Program integrates different programs permitting download and/or upload into the different
memories of the product.
First, it initializes the Debug Unit serial port (DBGU) and the USB Device Port.
Then the DataFlash Boot program is executed. It looks for a sequence of eight valid ARM exception
vectors in a DataFlash connected to the SPI. All these vectors must be B-branch or LDR
load register instructions except for the sixth vector. This vector is used to store the size of the
image to download.
If a valid sequence is found, code is downloaded into the internal SRAM. This is followed by a
remap and a jump to the first address of the SRAM.
If no valid ARM vector sequence is found, the DataFlash Boot program is executed on the second
chip select.
If no valid ARM vector sequence is found, NAND Flash Boot program is then executed.
The NAND Flash Boot program looks for a sequence of eight valid ARM exception vectors. If
such a sequence is found, code is downloaded into the internal SRAM. This is followed by a
remap and a jump to the first address of the SRAM.
If no valid ARM vector sequence is found, SAM-BA Monitor is then executed. It waits for transactions
either on the USB device, or on the DBGU serial port.
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