|
Message
From: rich_daddio at yahoo.com<rich_daddio@y...>
Date: Wed Jul 9 18:12:59 CEST 2008
Subject: [openrisc] GPIO interrupt handling?
MIPish but might be helpful.
http://strmnnrmn.blogspot.com/2006/05/branch-delay-instructions.html
Most MIPS docs contain pretty good explanations of architectural
reasons for delay slots and how to use and abuse them :).
The Hennessy books might have some good info too.
HTH,
Rich d
----- Original Message -----
From: Xiang Li<olivercamel@g...>
To:
Date: Wed Jul 9 12:03:41 CEST 2008
Subject: [openrisc] GPIO interrupt handling?
> Hi List,
>
> Actually I have the same question for a long time, i.e. could
> someone
> explain a little more about the delay slot to me? Becasue there 's
> too
> few explainations I can find from openrisc documents.
> As far as I know, all the the "l.jump" instructions will
> be followed
> one delay slot. The instructions stored in the delay slot will be
> performed beform the "l.jump". Do I understand correctly?
> If so, why
> do we have to design such a delay slot? what is it used for? why
> the
> l.jump have to performed after the instructions in the delay slot?
> And
> in the program I 've seen, more then 90% "l.jump" is
> followed by a
> "l.nop", so is the delay slot really necessary, why not
> combine the
> two together?
> I know this perhaps because of the pipeline of openrisc, but again,
> there's no more description for pipeline in the document. Thanks a
> lot
> for help.
> /Xiang
> On Tue, Jul 8, 2008 at 9:23 AM, Robert Cragie <rcc at
> jennic.com> wrote:
> > As you have put
> >
> > l.jalr r2
> > l.addi r2,r0,0
> >
> > then as far as I can see it you have set r2 to 0 in the delay
> slot, which
> > will be executed before the jump. Therefore you will be
> jumping to 0. Try:
> >
> > l.jalr r2
> > l.nop
> > l.addi r2,r0,0
> >
> > Also, maybe think about saving r2 on the stack in the ISR
> instead of just
> > clearing it.
> >
> > Robert
> >
> > silzon at naver.com wrote:
> >
> > Hello. I run or1200 RISC on Evaulation board.
> > I am programming GPIO interrupt system.
> > It work interrupt service routine, but,
> > After interrupt service routing is finished, It doen't return
> back!
> > my reset.S is..
> > .org 0x800
> > _hpint:
> > l.movhi r2,hi(_isr_gpio)
> > l.ori r2,r2,lo(_isr_gpio)
> > l.jalr r2
> > l.addi r2,r0,0
> > l.rfe
> >
> >
> > what's wrong??
> >
> >
> > please, help me :)
> > _______________________________________________
> > http://www.opencores.org/mailman/listinfo/openrisc
> >
> >
> > --
> > Robert Cragie, Design Engineer
> > Direct: +44 (0) 114 281 4512
> >
> _______________________________________________________________
> > Jennic Ltd, Furnival Street, Sheffield, S1 4QT, UK
> > http://www.jennic.com Tel: +44 (0) 114 281 2655 Confidential
> >
> _______________________________________________________________
> >
> > _______________________________________________
> > http://www.opencores.org/mailman/listinfo/openrisc
> >
>
>
|
 |
Browse
