Hi,

I know I'm probably having a complete blonde moment here, but it is my
understanding that when at the reset vector, we know that PCLATH has to be =
0, and the initialisation routine can always be placed within the first page
in program space. Hence, we can get by with a single GOTO at the reset
vector address, which branches to somewhere within the first page.

Please tell me what I've missed. Appologies in advance if this has been
discussed to death already.

Trev




> -----Original Message-----
> From: Olin Lathrop [SMTP:olin_piclist@EMBEDINC.COM]
> Sent: 17 June 2002 21:41
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]: Jtag  and more
>
> > That would definitely be a nice feature, and I think that they may be
> moving
> > towards it.  It looks to me like the '87x is designed to be forwards
> > compatible with a future MCU that has 4 interrupt source, considering
> that
> > it has the 3 empty blocks between the reset vector and the interrupt
> vector.
>
> No, that's so you can jump from the reset vector before the code hits the
> interrupt vector.  You need at least 3 instructions for this, two to set
> PCLATH properly, and one GOTO.  I use the 4th instruction to make sure
> interrupts are off so that a GOTO 0 (with PCLATH set appropriately of
> course) performs a software reset.
>
> > Some, yes, but most, probably not.  The PIC series was designed, for the
> > most part, to be a very inexpensive line of devices.  They wanted to
> build
> > for the common hobbyist that couldn't afford the the shiny new Motorola
> MCU.
>
> I rather doubt Microchip cares much about the .01% of PICs sold that are
> bought by hobbiests.  Hobbiests like PICs because they are targeted for
> low
> cost applications, and because Microchip learned early on that providing
> decent software tools for free helps to sell hardware.
>
>
> *****************************************************************
> Embed Inc, embedded system specialists in Littleton Massachusetts
> (978) 742-9014, http://www.embedinc.com
>
> --
> http://www.piclist.com hint: The list server can filter out subtopics
> (like ads or off topics) for you. See http://www.piclist.com/#topics
>

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.