reset vector on a 68hc11

[Roger Heflin]

On Fri, 25 Jun 1999, 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)
> 
> 
> > =========================================================== 
> > 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
> (613) 591-0931      (voice)         mail: 175 Terrence Matthews          
> (613) 591-3579      (fax)                 Kanata, Ontario, Canada K2M 1W8
> 
> 
THe chip in my 93 Z28 maps exactly like that.  The 32 kb prom is
mapped at 0x8000, and code starts at 0xA000 and the reset vector
points to 0xA000.   I have just been reversing it to commented pseudo
code and not worring about getting it to any specific langage, as when
I patch code I have just been putting a jump to the new code, putting
the code I want to replace or change things and then a jump back to
where it should be. 

			Roger
			http://www.hit.net/~rah