ATSAMA5D41A-CU View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'ATSAMA5D41A-CU' PDF : 1808 Pages View PDF
12. Standard Boot Strategies
12.1
Description
The system always boots from the ROM memory at address 0x0.
The ROM code is a boot program contained in the embedded ROM. It is also called “First level bootloader”.
This microprocessor can be configured to run a Standard Boot mode or a Secure Boot mode. More information on
how the Secure Boot mode can be enabled, and how the chip operates in this mode, is provided in the application
note “SAMA5D4x Secure Boot Strategy”, Atmel literature No. 11295. To obtain this application note and additional
information about the secure boot and related tools, contact an Atmel Sales Representative for further details.
By default, the chip starts in Standard Boot Mode.
Note:
JTAG access is disabled during the execution of ROM Code Sequence. It is re-enabled when jumping into SRAM
when a valid code has been found on an external NVM, in the same time the ROM memory is hidden. If no valid boot
has been found on an external NVM, the ROM Code enables the USB connection and the DBGU serial port, and then
waits for a special command to set the chip in Secure mode. If any other character is received on any of the two
connection link above, the ROM code starts the standard SAM-BA Monitor, locks access to the ROM memory and re-
enables the JTAG connection.
The ROM code standard boot sequence is executed as follows:
Basic chip initialization: runs on internal 12 MHz RC oscillator and PLL
Attempt to retrieve a valid code from external non-volatile memories (NVM)
Crystal or external clock frequency detection to get the clock accuracy required for USB connection
Execution of a monitor called SAM-BA Monitor, in case no valid application has been found on any NVM
12.2 Flow Diagram
The ROM Code implements the algorithm shown in Figure 12-1.
Figure 12-1. ROM Code Algorithm Flow Diagram
Chip Setup
Valid boot code
Yes
found in one
NVM
No
SAM-BA Monitor
Copy and run it
in internal SRAM
70 SAMA5D4 Series [DATASHEET]
Atmel-11238C-ATARM-SAMA5D4-Datasheet_12-Jul-16
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