N. Coesel wrote:
At 04:53 17-06-05 -0400, you wrote:
I'm trying to write a bootstrap routine in C that will reside in flash
and be copied to RAM for execution. Can anyone give me some helpful
hints on how to do that?
In an earlier discussion the method of copying a routine was discussed.
That should be the easy part. I wasn't worried about that, but I'll
check the archives just in case I'm missing something.
I've searched the docs for any reference to relocatable code (there will
be some subroutines, also in RAM) or preprocessor commands that might be
able to specify that this code will be running at a particular address
(in this case within the RAM) and haven't been able to find anything
that relates to this problem.
Why would you copy more than one subroutine in RAM? The only thing you will
want in RAM is the code that actually programs the flash. The amount of
memory doesn't allow for allocating large fixed buffers for this.
This BSL also needs to decrypt the data to be written to flash and
handle some handshaking with the PC. The decryption routine might be
erased at some point during the flash programming even if I only erase
the segment about to be written. That wouldn't be good. And, part of
the decryption algorhythm makes multiple calls to a subroutine, so that
inlining that code would increase the size - this might not be a
problem. I'm using an msp430x449 with 2k of RAM, so I think I'll have
plenty of space for code and a communications buffer.
So far, looking at the assembler output, it seems that calls are my only
problem - they use direct addressing. So, I can just "fix" these few
lines in the assembler or try indirect calls in C or just inline everything.
Dale Cunningham
