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=========================== APEX Boot Loader Release Notes & Quickstart =========================== The APEX boot loader has been designed to be small, efficient, and easy to extend. It uses some code and the build system from the Linux kernel. There are pieces of code taken from BLOB and UBoot as well. Newer Versions of APEX ---------------------- There is an ftp archive of APEX releases. <ftp://ftp.buici.com/pub/apex> There is also a wiki with information about APEX. <http://wiki.buici.com/wiki/Apex_Bootloader> Supported Targets ----------------- The loader is fully functional for the LPD79524, LPD7A400, LPD7A404, IXP42X. It builds for the LPD79520, but there is presently no version of the Linux kernel that recognizes the correct architecture number. APEX also builds for the MX31 and the S3C2410. Building APEX ------------- The config file has an option to define cross-compiler prefix. It must be set unless you are building on an ARM host platform. For example, CROSS_COMPILE=/usr/arm-linux/gcc-3.4.1-glibc-2.3.3/bin/arm-linux- The cross compiler may also be set in the environment or on the make command line. Doing so will override the value set in the configuration file. make CROSS_COMPILE=/usr/arm-linux/gcc-3.4.1-glibc-2.3.3/bin/arm-linux- Development proceeds with the 3.x compilers. GCC 2.95.3 does build APEX at a slight penalty in code size. Beware of GCC 2.95.3. It does not properly honor the naked function -------------------- attribute which means that it may improperly handle register allocation. The relocate_apex() function is vulnerable to the problem and may cause APEX to fail. If you must use GCC 2.95.3, make sure that there are no DEBUG_LL calls in relocate_apex(). Like the Linux kernel, building APEX requires a configuration file called '.config'. To build using the default configuration for the LPD79524: # make lpd79524_config To change the default configuration, use one of the configuration programs. # make xconfig APEX uses the Linux kernel build scripts so that rebuilding is as optimal as the kernel. Changes to the configuration are automatically propagated such that only affected source files are rebuilt. # make The ELF format binary, apex, as well as a link to the dumped apex.bin will be put into the root directory. Running APEX ------------ APEX is designed to start from any address and to relocate itself when necessary. If the binary is small enough (less than 16KiB), it may be copied to the internal SRAM of the LH79524 and executed from there. Once you see the apex> prompt, the loader may be copied to flash and the environment edited. Below is the signon message. It may be reprinted with the 'version' command. apex> ver APEX Boot Loader 1.0.6 -- Copyright (c) 2004 Marc Singer APEX comes with ABSOLUTELY NO WARRANTY. It is free software and you are welcome to redistribute it under certain circumstances. Refer to the source the COPYING for details. apex => mem:0x20200000#0x4a94 env => nor:128k#64k CPLD revision 0x5 The apex and env region specifications are important. The apex spec describes where in RAM apex has been relocated as well as the exact length of the program. The env spec describes where in flash the environment is stored. Assuming that APEX needs to be the first program in NOR flash, writing APEX to flash looks like this. apex> erase nor:0 apex> copy mem:0x20200000#0x4a94 nor:0 The source of the copy command is the descriptor from the signon message. Preparing the environment area is even simpler. apex> erase nor:128k#64k Again, using the information in the signon to erase the proper portion of flash. The environment allows APEX to be customized at runtime. o Bootstraping APEX with LOLO or a JTAG emulator o Downloading the kernel using XMODEM o Changing the startup command to copy the kernel to RAM o Changing the kernel command line o Changing the startup command to automatically boot the kernel Checksum Compatibility ---------------------- The checksum command built into APEX conforms to the POSIX.2 standard algorithm which is also used by GNU cksum. This is not compatible with the BSD sum command or with md5sum. Getting Help ------------ Beyond what is here, you can send mail directly to me, the author. Marc Singer <email@example.com>