ATSAMA5D35A-CU View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATSAMA5D35A-CU

SMART ARM-based MPU

Atmel Corporation 

The NVM bootloader program first initializes the PIOs related to the NVM device. Then it configures the right

peripheral depending on the NVM and tries to access this memory. If the initialization fails, it restores the reset

values for the PIO and the peripheral, and then tries to fulfill the same operations on the next NVM of the

sequence.

If the initialization is successful, the NVM bootloader program reads the beginning of the NVM and determines if

the NVM contains a valid code.

If the NVM does not contain a valid code, the NVM bootloader program restores the reset value for the peripherals

and then tries to fulfill the same operations on the next NVM of the sequence.

If a valid code is found, this code is loaded from the NVM into the internal SRAM and executed by branching at

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

calls to functions are PC relative and do not use absolute addresses.

Figure 11-4. Remap Action after Download Completion

0x0000_0000

Internal

ROM

REMAP

0x0010_0000

Internal

SRAM

0x0000_0000

0x0010_0000

0x0030_0000

Internal

ROM

Internal

ROM

0x0030_0000

Internal

SRAM

Internal

SRAM

11.4.3 Valid Code Detection

There are two kinds of valid code detection.

11.4.3.1 ARM Exception Vectors Check

The NVM bootloader program reads and analyzes the first 28 bytes corresponding to the first seven ARM

exception vectors. Except for the sixth vector, these bytes must implement the ARM instructions for either branch

or load PC with PC relative addressing.

Figure 11-5. LDR Opcode

31

28 27

24 23

20 19

16 15

12 11

0

1 1 1 0 0 1 I PU 1W0

Rn

Rd

Offset

Figure 11-6. B Opcode

31

28 27

24 23

0

11101010

Offset (24 bits)

68 SAMA5D3 Series [DATASHEET]

Atmel-11121F-ATARM-SAMA5D3-Series-Datasheet_02-Feb-16

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