Bootstrap -- System startup


The BMS signal to the CPU controls the initial system bootstrap selection. This is used in conjunction with the OTP (FUSE) on-chip configuration, and reset “input” pin state, to select the boot source for the CPU.

Table 241-1. BMS signal

BMS signal Description
BMS_BIT=0 The embedded (on-chip) RomBOOT first-level bootloader is used. The actual boot source used will depend on the presence of suitable binaries on the sources scanned by the RomBOOT code. The first acceptable binary is loaded into SRAM and executed. If no valid non-volatile-memory (NVM) binary is found then the RomBOOT will enter the Atmel SAM-BA monitor.
BMS_BIT=1 The application installed on the EBI_CS0 device is executed in-situ. The on-chip RomBOOT configures the chip-select for 12MHz RC access prior to executing the code mapped from address 0x00000000.

The “Standard Boot Strategies” section of the SAMA5D3 Series Datasheet provides details about the boot sequence configuration, and should be read in conjunction with this documentation.

The hardware platform documentation should be read in conjunction with this generic SAMA5D3 CPU documentation with regards to specific jumper settings that may affect the bootstrap code executed.

For some designs directly booting from an EBI_CS0 memory-mapped device is the simplest option. However, making use of the SAMA5D3 RomBOOT world to load a small second-level boot loader allows the easier possibility of providing support for in-field upgrades and selection of multiple application images.

Note: When BMS_BIT=1 and code is started from the EBI_CS0 device then the Atmel Secure Boot functionality is not available.

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