RP2040 Boot Sequence¶

Main Points

Boot sequence bifurcation

The RP2040 boot sequence divides into hardware and processor-controlled stages for systematic start-up.

Flexibility in external flash compatibility

Stage 2 boot configurations enhance compatibility with diverse external flash chips, offering flexibility in programming.

Precise initiation of user code

Detailed programming of exit routines and the reset handler ensures precise user code execution initiation.

Insights

The RP2040 boot sequence is bifurcated into a hardware-controlled and processor-controlled process, ensuring systematic powering and operation of peripherals.

The hardware-controlled boot sequence oversees safely initiating the minimum necessary peripherals for processor execution. Following this, the processor-controlled sequence directs the actual execution steps starting from ROM, including conditional process flow based on core identification and flags.

Configurations and compatibility for boot stage 2 highlight the RP2040's flexibility in dealing with external flash memory.

Boot stage 2 is managed by boot2 code, specifically tailored for compatibility with diverse external flash chips. The flexibility is further enhanced by allowing compile-time selection of boot2 code as per the flash chip, detailed through examples like setting the PICO_BOOT_STAGE2_CHOOSE_W25Q080 flag.

The exit routine from boot stage 2 and the reset handler design showcase meticulous programming to initiate user application code.

Detailed design in exit routines and the careful layout in reset handler operations illustrate a precise flow from system boot-up via stages to user code execution, with emphasis on memory initialization and platform-specific configurations.

Images

URL

https://vanhunteradams.com/Pico/Bootloader/Boot_sequence.html

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