Datasheet

SAM9261 [DATASHEET]

Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16

12.5 Serial Flash Boot

The Serial Flash boot looks for a valid application in the SPI Serial Flash memory.

SPI0 is configured in mater mode to generate a SPCK at 8 MHz. Serial Flash shall be connected to NPCS0.

The Serial Flash boot reads the serial flash status register (Instruction code 0x05). The serial flash is considered

as ready if bit 0 of the returned status register is cleared.

If no serial flash is connected or if it does not answer, Serial Flash boots exits after a 1000 attempts.

If the serial flash is ready, Serial Flash 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.

If a valid application is found, this application is loaded into internal SRAM and executed by branching at address

0x0000_0000 after remap. This application may be the application code or a second-level bootloader.

Figure 12-6. Serial Flash Download

End

Read the first 8 instructions (0x0b).

Decode the sixth ARM vector

Yes

Read the Serial Flash into the internal SRAM.

(code size to read in vector 6)

Restore the reset value for the peripherals.

Set the PC to 0 and perform the REMAP

to jump to the downloaded application

Send status command (0x05)

8 vectors

(except vector 6) are LDR

or Branch instruction

Yes

Start

Is status OK?

Jump to next boot

solution