Yeah, I always forget about IRP since I usually use the 873.

Regards,

Al Williams
AWC
* Floating point A/D
http://www.al-williams.com/awce/pak9.htm

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of David Duffy
> Sent: Tuesday, August 28, 2001 5:37 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: reverse indirect addressing
>
>
> Ha! You're dead right. You can still do it if you manipulate the FSR's MSB
> and the IRP bit if required. It depends on which RAM banks you
> want to use.
> Just do the fiddling where I but the bank1 & bank0 codes. I've previously
> done what Al said & used 2 pointers before. (located in the high 16 bytes)
>
> At 10:34 PM 27/08/2001 -0500, you wrote:
> >Hmmm... I'm a little bleary eyed, but I don't think INDR works that way.
> >INDR is one of those magic registers that is in every bank. So it doesn't
> >matter what RP0,RP1 is set to, INDR is always [FSR].
> >
> >To do what you want, you need to keep the FSR "pointers" in a
> shared address
> >(depends on what processor you are using, but they all have some
> bytes that
> >are in all maps). Then you would swap FSR in and out as needed.
> Sure, its a
> >bottleneck just like the W register, but that's how it works.
> >
> >Regards,
> >
> >Al Williams
> >AWC
> >* APP-II simplifies PIC development:
> >http://www.al-williams.com/awce/app1.htm
> >
> >
> > > -----Original Message-----
> > > From: pic microcontroller discussion list
> > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of David Duffy
> > > Sent: Monday, August 27, 2001 8:35 PM
> > > To: PICLIST@MITVMA.MIT.EDU
> > > Subject: Re: [PIC]: reverse indirect addressing
> > >
> > >
> > > At 01:44 AM 28/08/2001 +0100, you wrote:
> > > >Sorry, probably didn't make myself clear....
> > > >Specifically what I was trying to do was specify a register
> to be read
> > > >rather than reading from the INDR
> > > >
> > > >For example, if I have a block of registers set aside for some
> > > data, I can
> > > >clear sequential registers by:
> > > >
> > > >movlw MYFIRSTREG
> > > >movwf FSR
> > > >LOOP
> > > >movlw 0
> > > >movwf INDR
> > > >incf      FSR,1
> > > >goto    LOOP
> > > >
> > > >So this clears an infinite number of registers. In practice a
> > > quick decfsz
> > > >would limit it. In practice however, we often want to READ from
> > > one and copy
> > > >it into the next.
> > > >Clearly this could be done using
> > > >
> > > >movf READFROM1,F
> > > >movwf MOVETO1
> > > >movf READFROM2,F
> > > >movwf MOVETO2
> > > >.........
> > > >
> > > >etc, etc
> > > >But surely it would be better if an indirect addressing
> system or some
> > > >work-around meant you could avoid explicitly stating such
> commands. I ask
> > > >because I need to copy 96 registers from one page to another
> and I don't
> > > >want to end up writing 96*2 lines of code.......
> > >
> > > You can still use the FSR. Just keep 2 variables as pointers.
> > > Do the 2 banks of registers line up? (but on different banks)
> > > If so, you can do it in a loop, reading, changing bank, writing
> > > and changing bank back again each time. I haven't tested it
> > > but the below code should give you the idea.  :-)
> > >
> > > start:
> > >          movlw           .96
> > >          movwf           count
> > >          movlw           start_address
> > >          movwf           fsr
> > > loop:
> > >          movf            indf,w
> > >          bank1
> > >          movwf           indf
> > >          bank0
> > >          decfsz          count,f
> > >          goto            loop
> > > all_done:
> > >
>
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