13.6.2. Boot support

If there are two or more debug devices (for example, serial and serial/parallel), the boot agent must be able to receive messages on any device and then ensure that further messages that come through the channels layer are sent to the correct (new) device.

When the debug agent detects a Reboot or Reset message, it listens to the other channels using the device that received the message. All debug channels switch to use the newly selected debug device.

During debugging, each channel is connected through the same device to one host. Initially, Angel listens on all Angel-aware devices for an incoming boot packet, and when one is received, the corresponding device is selected for further Angel use. Angel listens for a reset message throughout a debugging session, so that it can respond to host-end problems or restarts.

To support this, the channels layer provides a function to register a read callback across all Angel-aware devices, and a function to set the default device for all other channel operations.

Copyright © 1997, 1998 ARM Limited. All rights reserved.ARM DUI 0040D
Non-Confidential