Hi List,
I'm coding some firmware for a pic18f2550 device with sdcc, using the
bootloader firmware provided by microchip.
The bootloader occupies 0x0 - 0x7FF, and expects the reset/interrupt vectors
to be at 0x800, 0x808, etc.
But sdcc/gplink seem to hardcode their location to 0x00, 0x08, 0x18.
I tried using a modified linker script with:
-----------------
...
CODEPAGE NAME=boot START=0x0 END=0x7FF PROTECTED
CODEPAGE NAME=vectors START=0x800 END=0x829 PROTECTED
CODEPAGE NAME=page START=0x82A END=0x7FFF
...
------------------
Which works only partially: The code is put into 0x82A..0x7FFF just fine, but
the vectors are still inside the boot page.
The only way I found to work arround that is to use #pragma code inside the
source, like:
-------------------
#pragma code high_isr_proxy 0x808
void high_isr_proxy(void) __naked interrupt 1 {
__asm goto _high_isr __endasm;
}
#pragma code low_isr_proxy 0x818
void low_isr_proxy(void) __naked interrupt 2 {
__asm goto _low_isr __endasm;
}
void high_isr(void) shadowregs interrupt {
...
}
void low_isr(void) shadowregs interrupt {
....
}
----------------------
Which seems to Do The Right Thing(tm) for interrupts, but for the startup code
I only could get it to work by linking a customized crt0i.c, with:
------------
/* prototype for the startup function */
#pragma code _entry 0x800
void _entry (void) __naked __interrupt 0;
------------
added.
While this works for now, I'd rather find a posibility to control the location
of the isr vectors entirely with the linker script, so the same source could
be used with and without a bootloader, by simply changing the .lkr file used.
Did I miss some option for sdcc/gplink, or is that currently not possible?
I'm using "sdcc 2.6.0 #4294 (Jul 23 2006)" and "gplink-0.13.3 alpha".
Thanks in advance,
/Ernst
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