Re: Addi on the AVR micro

[Denis Chertykov <denisc at overta dot ru>]

Jonathan Hunt <jhuntnz@users.sourceforge.net> writes:

> On Saturday 12 May 2001 15:48, you wrote:
> > Jonathan Hunt <jhuntnz@users.sourceforge.net> writes:
> > > Hi,
> > >
> > > The AVR has an instruction subi (subtract immediate) but no addi. So I
> > > use subi reg, -(num) to add immediate. However this poses a problem when
> > > you try and do it with a memory address like this:
> > >
> > >          .data
> > >          .org 0x00
> > >          __X_60:
> > >          mema:   ; Real address is 0x60, offset address is 0x00
> > >
> > >          .text
> > >          subi    r16, -mema      ; Generates an error
> > >          subi    r16, 0x100 - mema ; Generates an error
> > >          subi    r16, !mema + 1  ; Uses the offset address of mema for
> > > the ! which makes
> > >                                  ; it incorrrect
> > >          ; The only work around I have found
> > >          subi    r16, lo8(__X_60_ + (0xff - 0x60) - mema)
> >
> > Use "subi r16, lo8(-(mema))"
> >
> > Denis.
> 
> Thanks for the help but...
> 
> After all that I find out if I'd just have put brackets around the address it 
> would have work -- aargh!!! But why? Why does it require brackets? Is it 
> intentional?

It's because I wrote a bad syntax parser for the avr-as.

Denis.