MAIL_IN_CMD_SHIFT
in = MAIL_IN_CMD_FLASH_READ << MAIL_IN_CMD_SHIFT;
in = MAIL_IN_CMD_FLASH_WRITE << MAIL_IN_CMD_SHIFT;
in = MAIL_IN_CMD_FLASH_UPDATE_AUTH << MAIL_IN_CMD_SHIFT;
in = MAIL_IN_CMD_POWER_CYCLE << MAIL_IN_CMD_SHIFT;