> Ruben J=F6nsson wrote:
> > Inputs don't use the shadow register. Just read the port directly.
> > =

> > btfss/btfsc does ofcourse read the port but they don't write anything b=
ack so
> > there is no rmw issue here and it doesn't involve the shadow register a=
t all.
> > =

> > You can even read the outputs and verify that they are the same as the =
shadow
> > register.
> =

> But why doing that ?
> =

> If you *are* using a shadow register it's becuse they are
> *not* (or might not be) the same becuse of RMW issues. If
> they are always the same you don't have any RMW issue
> and you do not need the shadow register in the first place.
> =

> Jan-Erik.
> =


I mean that you could do it to verify that the outputs are as expected - no=
t =

for bit manipulations while setting the indiviual bits as part of the norma=
l =

operation. That would, as you say, defeat the whole meaning of using the sh=
adow =

register.

The port bits might not be the same as the shadow register bits if the outp=
ut =

is shorted or overloaded and you might want to take some action then. This =

check could be done periodically while not doing something else.

/Ruben
 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

-- =

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