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# 1.5.3 Serial Memory Bootloader Configurations

Bootloader Specific User Configurations

- Bootloader Serial Memory Used:

  - Specifies the Serial memory driver used by bootloader to receive the application
  - The name of the serial memory will vary based on the driver connected to bootloader

- Bootloader NVM Memory Used:

  - Specifies the memory peripheral used by bootloader to perform flash operations
  - The name of the peripheral will vary from device to device

- Bootloader Size (Bytes):

  - Specifies the maximum size of flash required by the bootloader
  - This size is calculated based on Bootloader type and Memory used
  - This size will vary from device to device and should always be aligned to device erase unit size

- Enable Bootloader Trigger From Firmware:

  - This Option can be used to Force Trigger bootloader from application firmware after a soft reset. It does so by reserving the specified number of bytes in SRAM from the start of the RAM. The reserved memory is updated by the application with a pre-defined pattern. The bootloader firmware in the bootloader_Trigger() routine, can check the reserved memory for the pre-defined pattern and enter bootloader mode if the pattern matches.

  - Number Of Bytes To Reserve From Start Of RAM:

    - This option adds the provided offset to RAM Start address in bootloader linker script.
    - Application firmware can store some pattern in the reserved bytes region from RAM start for bootloader to check at reset in bootloader_Trigger() function

Bootloader System Configurations

- Application Start Address (Hex):
  - Start address of the application which will programmed by bootloader
  - This value is filled by bootloader when its loaded which is equal to the bootloader size. It can be modified as per user need
  - This value will be used by bootloader to Jump to application at device reset

Bootloader MPLAB X Settings

- As the Serial memory may not have any valid binary required by bootloader for the first time, Adding the application to be bootloaded as loadable allows MPLAB X to create a unified hex file and program both these applications in their respective memory locations
  - By doing this, At first bootup bootloader directly jumps to application as the serial memory does not have any valid binary

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