I=B4m using the PIC18 TCP/IP boot-loader from Microchip, and it indeed is
almost transparent to the application developer.

The only change to the code one must do is to reduce the length of the
program FLASH segment in the linker-script, because the boot-loader
resides at the end of the flash memory.

The boot-loader then takes the first two instructions of the
application, saves them in an area inside itself followed with a jump to
the third instruction and replaces the original instructions with a jump
to its own start.

When calling the application, the boot-loader just jumps to the saved
original instructions.


William "Chops" Westfield escreveu:
> On Sep 30, 2008, at 9:47 AM, Byron Jeff wrote:
>
>   =

>> OTOH [a bootloader] can be completely transparent and accept  =

>> virtually any image unchanged.
>>     =

>
>
> How is this possible on a PIC?  Either you need to have code located  =

> at the reset vector, or you have to count on the code that IS at the  =

> reset vector behaving in a certain way (ie falling through into the  =

> bootloader elsewhere?)
>
>
>   =

>>  Teaching and learning are the goals.
>>     =

>
> Indeed; a class that starts off using a bootloader for "normal"  =

> embedded programs, and ends up explaining just what the bootloader  =

> does, how it works, and perhaps involves an assignment to WRITE a  =

> bootloader (for something simple, say an EEPROM) would be a pretty  =

> good class, IMO.
>
> BillW
>   =


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