gnupic: Bit variables in C
Subject:
Re: Bit variables in C
From:
Scott Dattalo ####@####.####
Date:
15 Nov 2000 13:30:33 -0000
Message-Id: <Pine.LNX.4.21.0011150730580.18530-100000@tempest2.blackhat.net>
On Wed, 15 Nov 2000, Scott Dattalo wrote:
> On Wed, 15 Nov 2000, Alex Holden wrote:
>
>
> > One problem, how do you represent a pointer to a single bit
> > variable?
>
> That's a good question. The short answer is I don't know (at least
> efficiently).
After I wrote this, I tried bit pointers with SDCC. It says:
t.c(21):error *** Array or Pointer to bit|sbit|sfr not allowed.'Pbit'
There, Problem solved!
The PIC code SDCC generates for bit addition is:
bit bit0 = 0;
bit bit1 = 0;
bit bit2 = 0;
bit1 = bit0 + bit2; // t.c line 25
; t.c 25
movlw (1 << (_bit1 & 7))
bcf (_bit1 >> 3), (_bit1 & 7)
btfsc (_bit0 >> 3), (_bit0 & 7)
xorwf _bit1,f
btfsc (_bit2 >> 3), (_bit2 & 7)
xorwf _bit1,f
BTW, I posted a challenge to the PICLIST to minimize this snippit. I'm probably
going to be posting many little challenges like this.
SDCC `bit' types will be supported in the PIC port of SDCC.
Scott
