----- Original Message ----- 
From: "Jan-Erik Soderholm" <jan-erik.soderholm@telia.com>
Subject: RE: [PIC]Initialised data initialisation


> Yes. code calling your "lookup table". Just as usual. The IDATA
> directive just helps creating the RETLW instructions (I think ! ).

Well, the dt directive will do that.  I did a little reverse engineering and
here is what I found.

Using an idata directive results in (at least) three program sections.  If
you use one idata, you get a .cinit section, a .idata section, and a
.idata_i section.   The second two sections get replicated for additional
(named) idata directives.

The .cinit section contains data in 16 bit words, organized as 2 retlw
instructions per word, low byte first.  The first value contains the number
of sections to initialize.  For each section, there are then three words.
In order, they are the address (in program memory) of the .idata_i section,
the address (in GPR memory) of the .idata section, and the length of the
section.

The .idata_i section contains a retlw instruction for each byte to be
initialized.

If you name an idata section, the section names become your name, and your
name _i. So

    b2   idata

causes sections named b2 and b2_i.

What isn't at all obvious to me is how to describe to the assembler the
addresses of these sections.  So it's not clear to me that this is even
useable from assembler, at least not without manually patching in the
address of .cinit.

Much simpler just to use dt.

--McD


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