> "Robert K. Johnson" <rkj1@IX.NETCOM.COM> wrote:
> Won't the FSR return a zero when read???

I wrote:
> Not quite.
>
> The FSR reads and writes just like a RAM location.  However, it controls what
> register can be accessed through INDF (address 0x00).  So what happens if you
> use FSR to point INDF to itself?  Rather than the part doing an infinite
> indirection chain, it just reads zero and ignores writes.

Robert replies:
> Isn't that the same thing???

No.  The FSR always reads back exactly what you write to it.  The FSR will
only read as zero if you write zero to it.

Repeating what I wrote before,
> So what happens if you
> use FSR to point INDF to itself?  Rather than the part doing an infinite
> indirection chain, it just reads zero and ignores writes.
I should clarify that this is what happens after you write 0x00 (the address
of INDF) to the FSR, then try to read INDF.  With FSR set to 0x00, INDF
reads as zero and ignores writes.  Under this condition, FSR will still
read as 0x00, but it will not ignore writes.  If you write something else
to FSR, and read FSR, it will read back what you've written.