At 21:40 02/23/99 +0000, Sam Powell wrote:
>Whats the deal with the 256byte memory segments.. They are not page
>boundries are they? i.e. why does it matter if i have a data table crossing
>its boundy?

when you jump into a table using a computed goto by writing to the PCL
register, the bits above the 8 bits in PCL (that's 256 addresses) are taken
from PCLATH. so it does matter if your table crosses a 256 byte boundary,
because then you need different values in PCLATH for one table.

>Also... since 11 bits is enough to address 2K, why does one have to mess
>with the PCLATH register when do inter-segment goto's /calls.

if you do only intra-page (note "intra", not "inter", and the 2k-segments
are called pages in pic-speak) gotos and calls, you don't need to mess with
the PCLATH register. if you do computed gotos by writing to PCL, you might
have to mess with it, even within a 2k page, depending on the 256
byte-segment your table is in. if you do inter-page calls and gotos, you
always have to mess with it.

ge