Re: [avr-libc-dev] rjmp across FLASHEND

[Joerg Wunsch]

As Bernhard Kuemel wrote:

> I could ask Atmel. They do respond to such questions. I'm pretty sure it
> is ok to jump across flashend.

I think that might be useful, just to be sure.

> Should the odd case happen, that the application starts beyond the
> range of rjmp I have to use jmp in the loader. This makes the loader
> bigger by one word and the reset rjmp changes by one word. So I have 2
> different rjmps which I have to consider as sync word. I want to
> minimize the number of sync words to make syncing most reliable.

OK, I see.

The following should be possible to work around the situation:

#include <avr/io.h>

        .global main
main:
        rjmp    beyond_vectors
        nop
/* vectors follow */
        jmp foo
        jmp foo

foo:    rjmp foo

beyond_vectors:
        jmp tinyloader


        .org FLASHEND+1-0x3e
tinyloader:
        rjmp    tinyloader

Btw., .org is a "DONT" in a relocation assembler.  Already during the
days of the venerable Z80, this was avoided.  The correct way would be
to establish a separate section, and then assign the section start
address to the linker either within the linker script, or from the
linker commandline.
--
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

----- End forwarded message -----

--
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)