User`s manual

ROMboot

1-14

ROMboot

Note The PowerPlus architecture boards do not execute a

configured boot routine.

ROMboot is a mechanism for booting an operating system from a

user-defined routine stored in ROM. ROMboot executes at power-

up (or optionally at reset) if it is configured and enabled in

parameters set with the ENV command. It may also be executed

with the RB (ROMboot) command.

Refer to Chapter 3 for information on setting the ENV command

parameters for enabling ROMboot.

For ROMboot to work, a ROMboot routine must be stored in the

FLASH memory to support it. If ROMboot code is installed, a user-

written routine is given control (if the routine meets the format

requirements). One use of ROMboot might be resetting SYSFAIL*

on an unintelligent controller board.

The NORB command disables ROMboot.

For a user's ROMboot routine to gain control through the ROMboot

linkage, four requirements must be met:

❏ Power must have just been applied (or at reset, if configured

to do so with the ENV command).

❏ Your ROMboot routine must be stored within the PowerPC

board FLASH memory map (or elsewhere in onboard

memory, if configured to do so with the ENV command).

❏ The ASCII string ÒBOOTÓ must be located within the

specified memory range.

❏ Your ROMboot routine must pass a checksum test, which

ensures that this routine was really intended to receive

control at power-up.

When the module is ready it can be loaded into RAM. Use the CS

command to generate, install, and verify the checksum.