4.2 Writing the Boot Configuration Word (BCW) to Fuse

If the BSCR_BUREG_VALID bit is not set, or if DISABLE_BSCR is enabled, BCW from Fuse will be used to configure the boot sequence. Refer to Figure 4-1.

CAUTION:
  1. Once a Fuse bit is set to 1, it cannot be reset. So cautiously select the appropriate external NVMs.
  2. Once DISABLE_BSCR is enabled, only BCW from Fuse will be used. So, it is highly recommend to set DISABLE_BSCR only during the production phase.
  1. Enable the internal RC clock before writing the Fuse.

    sam-ba -p serial -d sama5d29 -a internalrc

  2. Write the Boot Configuration Word to the Fuse.
    sam-ba -p serial -d sama5d29 -a bootconfig -c writecfg:fuse:JTAG_IOSET3,UART0_IOSET1,SDMMC0,SDMMC1,QSPI1_IOSET2,EXT_MEM_BOOT
    Note: To boot from external QSPI memory, refer to the steps in section 4.1.1.2 Booting from a QSPI Memory.

  3. Turn off the power and turn on it again.
  4. Read the Boot Configuration Word to the Fuse.

    sam-ba -p serial -d sama5d29 -a bootconfig -c readcfg:fuse

  5. Connect the USB-TTL cable to UART DEBUG (J28) on the SAMA5D29-Curiosity board.
  6. Open any serial terminal and connect it to an appropriate com port.

  7. Once connected successfully, reset the board. The terminal displays RomBOOT.