Andre Abelian wrote:

> 1) some one wrote a code for us based on interrupt and we started to
> have some problems.  After I looked at the code I noticed that there
> is no 0x04 vector at all.

  You are correct in that it must have an interrupt routine at $04 if it
uses interrupts.  That is not to say there will be an " ORG 0x04"
statement in the code however.  Are you sure the startup code at ORG 0
doesn't consist of three instructions followed by a GOTO?  The next,
perhaps un-labelled instruction is then the start of the interrupt code.

  If that isn't obvious, just post what the first eight or so
instructions of code actually are?

> 2) what is this code is going to do and when do you use it ?
>     movlw    512&0xFF

  Well, it would appear to evaluate to zero, but it may have meaning in
context.  If you wish to ask such questions, post a section of the code
including about five lines before and five lines after.

> 3) same thing with this one
>     movlw   .100>>8
> I know this means shift right and I checked it in MPLAB in w
> register I am getting 0.

  Yep, that's to what it would evaluate all right.

> what is the purpose and meaning of this when do I need to use it any
> example will highly appreciated.

  It's certainly not obvious.  Post a decent piece of code with that in
the middle and we might have a chance.
--
  Cheers,
        Paul B.