2.5.2. About boot after reset

There is one Cortex M3 CPU integrated into the IoT Subsystem. After CPU reset de-assertion the CPU starts fetching the addresses as follows:

  1. 0x00000000: Fetch the stack pointer to initialize the SP register

  2. 0x00000004: Fetch the reset vector and jump to the reset vector value

  3. Reset vector: Start boot code execution

Address 0x00000000 of the IoT Subsystem is mapped to the eFlash controller statically. It is therefore not possible to directly boot from ROM attached to the AHB expansion port.

eFlash reference cell erase is performed during wafer testing. If the flash is not empty, the factory reset must be applied before first use. Because the eFlash main array will be then be empty, the initial reset vector, SP and boot code must be written to eFlash through the debugger.

Note

An alternative way to load the Flash content after wafer testing is to preload it with the Flash DFT controller.

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