Here is what I think is a very simple way to understand RES. It applies to 
both absolute and relocatable modes.

RES simply advances the current location in the current section. For 
absolute mode that is always the one and only program section (kinda, see 
special note, below). In relocatable mode it is the pointer for whatever 
section is current (even if it is a code segment!!!!).

Thus:
    Res    D'10'

in a code segment , is effectively like:

    ORG    $+D'10'

(note: I do not know if $+D'10' is a valid argument to ORG in relocatable 
mode!)

SPECIAL NOTE:

Contrary to the documentation:
> 5.50.2 Description
>  <snip>
>   In non-relocatable code, <label> is assumed to be a program
>   memory address.

I think that RES could be used to allocate RAM addresses in absolute mode, 
to wit:

    ORG    X'20'

abc   res    3
def    res    1

    ORG    X'0'

Startup:
    goto    init

In absolute mode, the assembler can't tell one type of symbol from another, 
so it should happily be able to handle this. Note that no HEX output should 
be generated for the data area starting at X'20' since no code (data?) is 
emitted.

[This has not been tested!!]

Bob Ammerman
RAm Systems



-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist