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# 1.5.2 Serial Memory Bootloader Execution Flow

- On device reset after System initialize, the Bootloader task starts executing from the SYS_Tasks()

- Once the Serial Memory driver is ready, it retrieves the Meta Data from serial memory

  - If any error in reading the Meta Data it directly jumps Run application

- It checks if the Meta Data read is valid using the Prologue and Epilogue.

  - If valid:

    - It stores the application start address and application size from meta data which will be used during programming operation

    - Checks if the Update Required flag is set. If set it jumps to Programming step or continues to Trigger Check

  - If Invalid:

    - It continues to Trigger Check

Trigger Check

- If there are no conditions to enter the Firmware Upgrade mode, the Bootloader jumps to Run application
  - Refer to the Bootloader Trigger Methods for different conditions to enter Firmware Upgrade mode

Programming

- Starts reading the application binary from serial memory and perform erase/program operations on internal Flash

- Once programming is completed, it generates CRC32 on programmed space of internal Flash and verifies it against the CRC32 value stored in Meta data

- Once verification is complete it clears the update required flag in meta data and triggers reset to Run application

Run Application

- The application start address used to jump to application space can be:

  - Application start address generated during compile time or

  - Application start address retrieved from valid Meta Data

- Calls SYS_DeInitialize() function to release resources used

- Jumps to application space to run the updated application

Rev: G