39.11.1 Boot Procedure, Processor Mode

  1. Configure the HSMCI data bus width programming SDCBUS Field in the HSMCI_SDCR. The BOOT_BUS_WIDTH field located in the device Extended CSD register must be set accordingly.
  2. Set the byte count to 512 bytes and the block count to the desired number of blocks, writing BLKLEN and BCNT fields of the HSMCI_BLKR.
  3. Issue the Boot Operation Request command by writing to the HSMCI_CMDR with SPCMD field set to BOOTREQ, TRDIR set to READ and TRCMD set to “start data transfer”.
  4. The BOOT_ACK field located in the HSMCI_CMDR must be set to one, if the BOOT_ACK field of the MMC device located in the Extended CSD register is set to one.
  5. Host processor can copy boot data sequentially as soon as the RXRDY flag is asserted.
  6. When Data transfer is completed, host processor shall terminate the boot stream by writing the HSMCI_CMDR with SPCMD field set to BOOTEND.