Re: [fpu] FPU operations

[Jamil Khatib <jamilkhatib75@yahoo.com>]

So I have to provide exception signals on the FPU
interface and the CPU core has to provide mask unmask
operation and generate interrupts but what about
rounding modes does the core need to provide the
signals

Also compare results status register?

I do not know if there are more registers to have
later

Should I provide all these signals

regards
Jamil


--- Damjan Lampret <damjanlampret@yahoo.com> wrote:
> Trust me. Exceptions are detected only by the CPU
> core (FPU doesn't
> know anything about exceptions). What FPU must
> signal is a cause for
> exception. So what I need from the FPU is a signal
> that represents
> particular cause for exception. This signal is for
> example OVERFLOW.
> Another is DIVIDE_BY_ZERO. Basically status bits
> that are generated
> together with the result of operation. CPU then
> takes appropriate
> actions to execute proper exception handler. So FPU
> doesn't even need
> to have their own CPU "visible" registers.
> 
> --damjan
> 
> --- Jamil Khatib <jamilkhatib75@yahoo.com> wrote:
> > 
> > --- Damjan Lampret <damjanlampret@yahoo.com>
> wrote:
> > > 
> > > > operations, but what about all status and
> control
> > > > registers? I'll put all of them internallay in
> the
> > > FPU
> > > > but we need to define a method to access them
> > > > 
> > > 
> > > Signals representing status bits should be
> > > registered outputs of FPU.
> > > It is up to FPU's boss (OR1K for example) to
> check
> > > and act accordingly
> > > (generate exceptions if necessary etc.). OR1K
> has
> > > its own instructions
> > > to operate over special purpose registers.
> > > 
> > > --damjan
> > > 
> > I am not sure if this is going to work, The
> exceptions
> > should be generated from the FPU (interrupt) and
> all
> > other registers, unless you want to provide a
> signal
> > interface for each exception, mask , compare.....
> > 
> > 
> > Regards
> > Jamil Khatib
> > 
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> 
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