Dmitry Kiryashov <PICLIST@MITVMA.MIT.EDU> wrote:

> I understand how RLF FILE,F command work but i have real puzzle when
> i try to think what RLF(RRF) STATUS,F(W) commands do ? ;)

... and he got a whole BUNCH of responses, all of which I've deleted,
so I'm not sure if anyone actually got it right.

Anyway... If the STATUS register holds ABCDEFGH before the
operation, here's what happens after the various RLF/RRF
instructions:

    After RRF STATUS,W:

        STATUS = ABCDEFGH (unchanged)
             W = HABCDEFG (exactly what you'd expect, if you remember
                 that STATUS.0 and the Carry flag are the same thing)

    After RLF STATUS,W:

        STATUS = ABCDEFGH (unchanged)
             W = BCDEFGHH (again, exactly what you'd expect given
                 that STATUS.0 is the Carry flag)

    After RRF STATUS,F:

        STATUS = HABDEFGH (just as we saw above, the MSB gets a copy
                 of the Carry flag.  /TO and /PD don't change, since
                 they're read-only, and DC, Z, and C don't change
                 because their protected by logic within the PIC)

    After RLF STATUS,F:

        STATUS = BCDDEFGA (this one's interesting... I wouldn't have
                 expected STATUS.0 to have changed, but it does [at
                 least on the emulator])

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499