reset vector on a 68hc11

[Steve Ravet]

Pat Ford wrote:
> 
> Previously, you (David Cooley) wrote:
> > At 10:36 AM 6/25/99 -0400, you wrote:
> > >Hi all:
> > >
> > > This may seem like a simple question but here goes, this is the last line
> > >of the
> > >bin file I'm looking at:
> > >000003ff0:  60 00 A1 DA A1 F7 60 00  A0 00 A0 00 A0 00 A0 00
>    ^^^^^^^^^ should be 7ff0 ( I loaded the file in the middle.. DOOH)
> > >
> > >the a0's are the reset vector right? is that a relative or absolute jump.
> > >ie does the reset jump to 3f58 ( 3ff0 - a0) or to 20a0 ( A0 + 2000)
> >
> > Depends...  Reset vector should be at address FFFE-FFFF... is this prom
> > mapped so it's address 3FFE-3FFF is actually the processors FFFE-FFFF?
> > If not, the reset vectors are contained in onboard ROM or the CPU's
> > embedded ROM.
> > If this was really the FFFE-FFFF in the CPU, the A000 would be the absolute
> > address of the beginning of the reset code.
> 
> so then if the eprom is mapped in so the reset vector is at fffe-ffff
> I should subtract 7fff from A000 to get the position of the reset code in
> the eprom ( 0x2000) right. What I'm trying to do is get a good asm listing
> and reverse it to C ( I'm working backwards from gcc for 68hc11)

No, whatever value is stored is 0xfffe-0xffff from the cpu's point of
view is the reset vector.  There is nothing relative about it.  The CPU
fetches the address from 0xfffe-0xffff, then starts fetching
instructions from the address listed there.

If your prom isn't mapped to the end of memory then the reset vector
isn't in the PROM image at all.  If it's a C3, then the reset vector is
in a ROM soldered to the board, not the PROM.  P4, I believe, has
everything in the PROM so the reset vector should be at the very end.

--steve

> 
> > ===========================================================
> > David Cooley N5XMT Internet: N5XMT at bellsouth.net
> > Packet: N5XMT at KQ4LO.#INT.NC.USA.NA T.A.P.R. Member #7068
> > We are Borg... Prepare to be assimilated!
> > ===========================================================
> >
> 
> --
> Pat Ford                           email: pford at qnx.com
> QNX Software Systems, Ltd.           WWW: http://www.qnx.com
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--
Steve Ravet
sravet at arm.com
Advanced Risc Machines, INC
www.arm.com