Sorry about the name cock-up Clyde.  How embarrasing.

OK, I've just tried this code:
#include <pic.h>

unsigned int count;

void main( )
{
        count = (CCPR1H << 8) + CCPR1L;
}

Compiled through MPLAB which produces the following command line:
C:\HT-PIC\BIN\PICC.EXE -Gmicrochip -O -Zg9 -D24 -16F877 -C -IC:\HT-PIC\INCLUDE -ASMLIST C:\HT-PIC\PROJECTS\MISC\TEST.C

This gives me:

        movf    22,w    ;volatile
        movwf   btemp+1
        clrf    btemp
        movf    21,w    ;volatile
        addwf   btemp,w
        movwf   _count
        movf    btemp+1,w
        btfsc   3,0
        incf    btemp+1,w
        movwf   _count+1

I was sure I must be doing something screwy here, so I have re-installed V8.75 just to make sure I had the right version and the results are the same.

Your idea of using it directly is superb, I just wouldn't have thought of that.  However it obviously only works in the minority of cases, a more general solution is needed for most jobs.

Regards

Mike Rigby-Jones

-----Original Message-----
From:   Clyde Smith-Stubbs [SMTP:clyde@HTSOFT.COM]
Sent:   Wednesday, March 22, 2000 10:55 AM
To:     PICLIST@MITVMA.MIT.EDU
Subject:        Re: 16-bit arithmetic in C

On Wed, Mar 22, 2000 at 09:51:16AM -0000, Michael Rigby-Jones wrote:
> It certainly would make a neat macro if it worked.  However, I've just tried
> it on V7.85, compiling for a 16F877 with maximum optimisation and it got
> it's knickers in a twist:

You didn't show your C code, but here's what I tried:

;x.c: 7: count = (CCPR1H << 8) + CCPR1L;
        movf    22,w    ;volatile
        movwf   _count+1
        movf    21,w    ;volatile
        movwf   _count

Looks fine to me.

Of course, the other (better) way to do it, which works since CCPR1L and
CCPR1H are adjacent and in the right order, is this

static unsigned int     CCPR1 @ 0x15;

Now you can just use it directly.

Regards, Clyde

PS - Mick, I don't think Clive James reads the PIClist.

--
Clyde Smith-Stubbs               |            HI-TECH Software
Email: clyde@htsoft.com          |          Phone            Fax
WWW:   http://www.htsoft.com/    | USA: (408) 490 2885  (408) 490 2885
PGP:   finger clyde@htsoft.com   | AUS: +61 7 3355 8333 +61 7 3355 8334
---------------------------------------------------------------------------
HI-TECH C: compiling the real world.