Re: [Simulavr-devel] modification of AVR simulator for SCA

[Thomas K]

Hi Jörg,

attiny2313 is tricky, the "old" ones initialized the SP to 0 (datasheet 
04/06), the attiny2313a (and attiny4313 also) initialized to RAMEND! 
(datasheet 11/09)

I've implemented it now for tiny2313 with RAMEND.

cu, Thomas


Am 18.02.2016 um 09:12 schrieb Joerg Wunsch:
> As Albrecht Frenzel wrote:
>
> > Chapter 7.5.1 "SPH and SPL – Stack Pointer High and Stack Pointer
> > Low Register" of the atmega 48/88/168/328 says, that the initial
> > value of SP is RAMEND.
> That's the case on all newer AVRs.
>
> The distinction between the architectures that initialize SP in
> hardware and those that don't is about the same where the three RC
> oscillators have been replaced by a single one, plus a prescaler (and
> the CKDIV8 fuse).  ATmega8, ATmega128, ATmega16, ATtiny2313,
> AT90CAN128 start with SP = 0, ATmega1281, ATmega88, ATmega164,
> ATtiny25 start with SP = RAMEND.
>
> I think SimulAVR should correctly simulate this different behaviour.
> Since the datasheet describes it, the user is allowed to rely on it.
>
> > Testing for 0 != SP_value only makes sense on instructions, that use
> > the content of SP.
> I agree.