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Baljit, This is my understanding of the terms, and a short tutorial on the functions. I hope that its not quite more than you wanted to know. I trust that others will note inaccuracies and differences in their understanding of the terms. "Startup Code" is a generic name for code that runs when the system starts up, typically after power on. A "Bootstrap Loader" is a particular kind of startup code that runs when a system starts up, that will reprogram the application code in flash memory if asked. In automotive systems, a "bootstrap loader" is common, because the HC-12 is sealed in a box, and it is much less expensive for the dealer to plug into a network somewhere in the car and reprogram one the mob of computers in the car than it is to have to get the offending box and plug into it. Because of this and security requirements, these bootstrap loaders may be rather elaborate. (The term "bootstrap" has long usage with computers. It comes from the idea that a minimal loader can load a much larger and useful program into memory in a process similar to "lifting oneself by one's bootstraps".) On the HC12, "startup code" often refers to assembler code that does things to make it possible for a compiled C program to run. Sometimes "initialization code" is used in contrast to refer to C code that sets up IO devices and system variables. This code runs after the assembler code has prepared the CPU to run C code. Required Tasks for HC-12 "startup code" -------------------------------- Write the INITRM register so that it is defined, and its "write-once" property is activated. This fixes the location of RAM in memory. Set the stack pointer (SP) register so that the CALL, JSR, PUSH and POP instructions will work as expected. Typical Additional Tasks for "startup code" ------- (These may be written in C once the RAM location is fixed and the stack pointer are set.) Write the INITRG register so that the register block has a fixed location. Write the MISC register so that the flash window from 0x4000 to 0x7FFF is defined as flash, or not. Write the INITEE register so that the EEPROM has a fixed location. Write the COPCTL register to make sure that the COP watchdog timer is running for normal operation, or not running for debugging. Note that the above functions need to have matching provisions in the linker directive file so that the application code is linked with the proper addresses. This is a frequent source of problems when starting to debug a new application. Bootstrap Loaders ----------------- There has been a lot of discussion with "bootloader" or "bootstrap loaders" in this list. A recent long discussion had the subject "HC12 flash reliability" because a question about flash reliability turned out to be raised by the behavior of a particular bootstrap loader. If you want to know more about bootstrap loaders, look in the mailing list archives for these subjects. Unfortunately, the automotive bootstrap loaders seem never to be discussed. Hope this helps, Steve Russell Nohau Emulators At 09:14 AM 12/31/2004, B singh <> wrote: >Hi, there > >What is the difference between Startup code and >Bootloader? > >If any body can hellp > >thanks >Baljit > >__________________________________ > > >Yahoo! Groups Links > > |