at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 77

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

13.6
6384B–ATARM–15-Dec-08
DataFlash Boot Sequence
Figure 13-6. Serial Flash Download
The DataFlash boot looks for a valid application in the SPI DataFlash memory.
SPI0 is configured in master mode to generate a SPCK at 8 MHz. DataFlash shall be connected
to NPCS0 or NPCS1.
The DataFlash boot reads the DataFlash flash status register (Instruction code 0xD7). The Data-
Flash is considered as ready if bit 7 of the returned status register is set.
If no DataFlash is connected or if it does not answer, DataFlash boot exits after 1000 attempts.
If the DataFlash is ready, DataFlash boot reads the first 8 words into SRAM (Instruction code
“Continuous Read Array” 0x0b) and checks if it corresponds to valid exception vectors according
to the Valid Image detection algorithm.
Read the SerialFlash into the internal SRAM.
Restore the reset value for the peripherals.
Set the PC to 0 and perform the REMAP
to jump to the downloaded application
Read the first 8 instructions (0x0b).
(code size to read in vector 6)
Send status command (0x05)
Decode the sixth ARM vector
(except vector 6) are LDR
or Branch instruction
Is status OK ?
8 vectors
Start
End
Yes
Yes
AT91SAM9G20 Preliminary
No
No
Jump to next boot
solution
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