Hi Peter,
> If I allow the linker to assign the location:
> lcd_t lcd;
> everything compiles fine. The lcd structure, is of course, not at the
> port address. If I
> volatile lcd_t __at (PORTB_ADDR);
> I get an error saying "multiple sections using address 0x6"
>
> But, I can declare:
> __sfr PORTB;
> _PORTB_bits_t PPORTB_bits;
> and use them as expected.
>
> What I don't understand (among a quadzillion things) is why can I use
> PORTB and PORTB_bits and not get that error, but if I use lcd to refer
> to port b bits, I get the above error. ggggrrr!!
PORTB and PORTB_bits are declared in the same .c file (pic16fXXX.c), so
they get allocated into the *same* section for the linker to place. If
you add another object at the same address in your .c (myproject.c), it
ends up in a *different* section that is to be placed at the same
address already occupied by the section containing PORTB and PORTB_bits.
Preprocessor to the rescue: Use the beautiful and quite intuitive =:-]
#define lcd (*(volatile __data lcd_t *)(PORTB_ADDR))
void
main (void)
{
lcd.rs = 1;
if (lcd.e) {
lcd.d = 1;
} // if
}
to get where you want, though the code is considerable larger than when
accessing PORTB_bits. There is still a lot of optimization potential.
Alternatively you could file a feature request with the gputils team to
add an option to allow overlapping sections. SDCC cannot do anything
about this problem.
Regards,
Raphael
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