I have a customer who will be using Hitech C on a project, and I will
be writing a bootloader so they can load the compiled .hex files into
the product in production. I don't have the time to get into learning
the innards of the C system at the moment, and my customer is new to C
and PICs, so I was wondering if any Hitech C users had a quick answer
to the following :=20

My bootloader (to be adapted from a previous product) uses the first 4
and last 256 program words - it is jumped to on reset, determines
whether or not someone is trying to send it some code up the serial
port, and if not, jumps into the  main application code.=20

The main issue is that the Hitech compiler will put its own code at
locations 0 to 3, presumably just setting the page preselect bits and
jumping to its start entry point.=20

With the bootloader present, the code in these locations needs to jump
into the bootloader, and the bootloader then needs to know where in
memory the C code entry point is. =20

I see 2 solutions :=20
1) Can Hitech C (presumably the library or link configuration) be
_easily_ tweaked to tell it to put the entry to it's startup code at a
specific FIXED  address (e.g. just before the bootloader), so the
bootloader  knows that by jumping to this address it will start the C
application.

Any pointers on how to go about doing this (if possible) would be
appreciated - I know from experience with another (non-PIC) C system
that it can take ages to track down how and where to do subtle tweaks
like this in the mass of make, config and header files that comprise
the avarage C project!

2) My PC software that talks to the bootloader can look at the first 4
words of the .hex object code it's being asked to download, and
relocate it to a fixed address known by the bootloader. This assumes
that C will generate a reasonably constant set of instructions for
these 4 locations, although the jump target address may be different.
This is not a problem, although it gets more messy if this target
address may be on a different page, or the optimiser is trying to be
clever by squeezing the odd instruction into any spare locations
within the first 4 words. .=20
Does Hitech C always generate  a fixed set of instructions at the
reset vector like this?(or can it be forced/tricked into doing so?)

Also, how do you tell Hitech C not to use the last 256 (or whatever)
words of program memory?

Obviously by C, I mean the whole compile-link process.=20
=20
Thanks in advance for any hints.=20

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