John Piccirillo wrote :

> >Yes, since it has the same address as "RESET_VECTOR".
> 
> Sorry, a typo.  I did use INT_VECTOR     CODE    0x004 followed by
> a simple ISR, just context saving, [code below] but the 
> assembly error was:

OK. You better cut-n-paste in the future. Or review your posts
a second time before hitting send... :-)

> Error - section 'INT_VECTOR' can not fit the absolute section.
> Section 'INT_VECTOR' start=0x00000004, length=0x00000010

Of course, the section is 10 bytes (as the message above says)
and if you add more code then that, you get that message. No
problem with that.

> > The CODE is used anywhere where you wan't to start a new 
> > code segment.
> 
> I hope you have the patience to tell me how that is used.  
> Where would
> it be useful to have different CODE sections.

Different CODE sections will be separatly listed in the MAP file
so you get sizes calculated "for free".
Separatly CODE sections will be individualy placed in the program
memory by the linker. So one can place a hardcoded table in the
middle of the program address area, and the linker will nicely
spread the code segments around that.
If you arrange your source code using multiple ASM files, you
*must* have at least *one* CODE segment/diretive per file (but
can have more then one to make the "job" for the linker easier,
the code more structured and the output of the linker a bit more
"usuable").

> Please feel free to comment on the form of the code.  How do I treat
> the portb equate,

What is "the portb equate" ? PORTB is PORTB...

> RES doesn't seem to work.

RES have noting to to with the SFR's !
You use RES to allocate your variables from the GPR's ("RAM").

> If I follow the 
> interrupt vector with a goto iserv and put the ISR down under Main Code, 
it
> assembles.

As expected...

> 
>     list      p=16F84
>          #include <p16F84.inc>

First, if you don't have any *specific* reason to use the
old/costly F84, make yourself a big favour and use
somthing modern. If it's for general PIC learning, maybe
a rather simple 16F628A would work (still can a lot more
then the F84 at half the price...).

> 
> INT_DATA                UDATA   0x0C
> portb                   equ             0x06

PORTB is defined in p16F84.inc. Remove that EQU !!

> w_temp          RES     1               ; variable used for 
> context saving
> status_temp             RES     1               ; variable 
> used for context 
> saving

Yes, that's right. See the MAP file to see the "real" addresses, (even
if they realy doesn't matter...).

> 
> ;*************************************************************
> *********
> RESET_VECTOR  CODE              0x000
>                          goto    start
> 
> INT_VECTOR      CODE    0x004
> 
>                  movwf   w_temp
>                  movf    STATUS,w
>                  movwf   status_temp
> 
> ; isr code can go here or be located as a call subroutine elsewhere

Yes, *if* shorter then the lenght of section "INT_VECTOR" in
the linker script (see the LNK file).

> 
>                  movf    status_temp,w
>                  movwf   STATUS            ;
>                  swapf   w_temp,f
>                  swapf   w_temp,w
>                  retfie
> 
> MAIN    CODE
> start           movlw   0x00
>                  tris    portb

TRIS is an "depricated" assembly instruction. Maybe not in the
F84 data sheet, but in practicly any other data sheet from a current
PIC type. Use MOVWF TRISB, instead.

>                  movlw   0x0f
>                  movwf   portb
> 
> circle  goto    circle
> 
>                  END
> 


Regards,
Jan-Erik.



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