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USING A BOOT MONITOR IN EMBEDDED SYSTEMS

Part 2ýBuilding on the Basics
by Ed Sutter

Start ý The Ethernet Interface ý The Command Line Interface ý "Get Your Tokens Here" ý One Last Topic About CLI ý Executable Scripts ý Application-to-Monitor Hook-Up ý The Moncom() Function ý The Monconnect() Function ý Letýs Regroup ý Xmodem and Tftp ý OK, Iým Done! ý Sources and PDF

THE ETHERNET INTERFACE

The Ethernet interface now can be initialized using getenv() to retrieve the content of the shell variables IPADD, GIPADD, NETMASK, and ETHERADD. The content of each of these shell variables is used to help initialize the interface. Obviously, the code must be prepared for the case of a nonexistent shell variable or invalid value by using some hard-coded default or treating this as an error. Note that this is allowing the same boot monitor binary to be used on multiple iterations of a hardware platform that has no special facility for storing this information. You can create this file with the monitorýs built-in file editor or it can be downloaded via XMODEM or TFTP. As you will see, this file then can be password-protected because the monitor also has four built-in user levels and each file can be created to be accessible only at a specified user level or above.

TFS is established, the monrc file has been executed, and the Ethernet interface has been configured based on shell variables set up in the monrc file. The generic system initialization has been completed. The final step would be to look through the file system once again for any auto-bootable files and run them. TFS provides this autoboot capability and allows the files to be executable binaries or scripts (as was the case earlier with the monrc file). The files are scanned in alphabetical order for any auto-bootable files, and execution depends on the content and flags of the file(s). For this article, letýs assume there are no auto-bootable files. This means that the next thing seen is the command line.

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