Atmel Evaluation Kit AT91SAM9X35-EK AT91SAM9X35-EK Data Sheet
Product codes
AT91SAM9X35-EK
54
SAM9X35 [DATASHEET]
11055E–ATARM–10-Mar-2014
Figure 11-4. Remap Action after Download Completion
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.
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
Figure 11-6. B Opcode
Unconditional instruction: 0xE for bits 31 to 28
Load PC with PC relative addressing instruction:
Rn = Rd = PC = 0xF
I==0 (12-bit immediate value)
P==1 (pre-indexed)
U offset added (U==1) or subtracted (U==0)
W==1
The sixth vector, at offset 0x14, contains the size of the image to download. The user must replace this vector with the
user’s own vector. This information is described below.
user’s own vector. This information is described below.
REMAP
Internal
ROM
Internal
ROM
0x0010_0000
0x0000_0000
Internal
SRAM
0x0030_0000
Internal
SRAM
Internal
ROM
0x0010_0000
0x0000_0000
Internal
SRAM
0x0030_0000
31
28 27
24 23
20 19
16 15
12 11
0
1
1
1
0
0
1
I
P
U
1
W
0
Rn
Rd
Offset
31
28 27
24 23
0
1
1
1
0
1
0
1
0
O set (24 bits)