On Sat, 15 Apr 2000, Paul B. Webster VK2BZC wrote:

> Scott Dattalo wrote:
>
>  (Obsequious comments glossed over)

You know, I didn't have to look that word up since I just learned it a couple of
days ago! (But how do you pronounce the damn thing? :)

>
> > Incidently, the TRIS instruction AFAIK is available on the f877 (at
> > least it is in gpsim).  A quick glance at the data sheet shows that it
> > isn't.
>
>   Not so.  In fact, the opposite, but oh, so subtly.
>
>   In all 14-bit series parts, TRIS and OPTION aren't confessed in the
> instruction set tabulation, but appear with the bizarre petulant
> "warnings" about the possibility of non-compatible vapourware in the
> imagined future; in the detailed instruction descriptions.
>
>   It gets worse!  I just browsed DS35007A-page 33 (PIC16F84A), which
> contains the apocryphal: "Note: To maintain upward compatibility with
> future PIC16CXXX products, do not use the OPTION and TRIS instructions."
>
>   Since this document does *not* contain the full instruction
> description, (refers rather to DS33023) it certainly doesn't help you to
> understand TRIS and OPTION, *however*, and I have to laugh, because on
> page 32 it contains the every-bit-as-sensible advice: "Note: Microchip
> does not recommend code protecting windowed devices."
>
>   I really think that says it all.
>
>   To remain on track however (forever difficult), the PIC16F87X
> datasheet DS30292A contains the admonishment about TRIS and OPTION,
> which de facto *confirms* that they are there.  I really wonder why on
> these parts they *didn't* remove that functionality.  Is it because they
> actually wouldn't *dare* present a blatantly sub-functional part to an
> ever more discerning market (notably: this list)?

I don't think they'll ever get rid of them. Perhaps they should abandon the
useless warnings... The good news is that I know there's one less bug in gpsim.

Scott