Actually - it could in fact be me who is confused.

I cheerfully admit that I don't grok "C".  What I was commenting on=20
was that register RA is in RAM Page 0 while TRISA is in RAM Page 1.

If that's not what you are doing, then I got it wrong.

dwayne


At 11:02 AM 4/22/2015, Nathan House wrote:
>Accidentally hit ctrl+enter, which sends the email in gmail :-/
>
>Attempt #2:
>
>I'm a little confused by your statement. Since the structs are unioned
>together, setting a bit inside either of them:
>
>TRISAbits.RA0 =3D 1;
>TRISAbits.TRISA0 =3D 1;
>
>Sets the same bit in memory.
>
>Can you elaborate what you mean when saying "the registers are at the same
>address in different RAM pages"?
>
>Thanks!
>
>Nate
>
>I'm a college student, take it easy on me ;-)
>
>Check out my small hobby electronics business!
>www.foxytronics.com
>
>On Wed, Apr 22, 2015 at 12:59 PM, Nathan House <nathanpiclist@gmail.com>
>wrote:
>
> > >Note that your first example (RA & TRISA) are *not* the same
> > >thing.  Yes - the definitions are the same but the registers are at
> > >the same address in different RAM pages.
> >
> > I'm a little confused by your statement. Since the structs are unioned
> > together, setting a bit inside them via one of these statements:
> >
> >
> > ----
> >
> > I'm a college student, take it easy on me ;-)
> >
> > Check out my small hobby electronics business!
> > www.foxytronics.com
> >
> > On Wed, Apr 22, 2015 at 11:22 AM, Dwayne Reid <dwayner@planet.eon.net>
> > wrote:
> >
> >> A couple of reasons.
> >>
> >> 1) Microchip has changed the names of certain registers and bit names
> >> over the years.
> >> 2) Legacy code written before those names were changed will compile
> >> cleanly and give the same results.
> >>
> >> I do the same thing in my code: I'll include defines for each of the
> >> different names that I've used over the years but changed along the wa=
y.
> >>
> >> Note that your first example (RA & TRISA) are *not* the same
> >> thing.  Yes - the definitions are the same but the registers are at
> >> the same address in different RAM pages.
> >>
> >> That said: I use exactly those same shortcuts in my code.  I simply
> >> ensure that I am on the correct RAM page when doing so.
> >>
> >> dwayne
> >>
> >>
> >> At 11:59 AM 4/20/2015, Nathan House wrote:
> >> >Hi,
> >> >
> >> >The main.pre file in my MPLAB X project seems to show the definitions=
 for
> >> >the configuration registers. One example is this:
> >> >
> >> >typedef union {
> >> >struct {
> >> >unsigned TRISA0 :1;
> >> >unsigned TRISA1 :1;
> >> >unsigned TRISA2 :1;
> >> >unsigned TRISA3 :1;
> >> >unsigned TRISA4 :1;
> >> >unsigned TRISA5 :1;
> >> >unsigned TRISA6 :1;
> >> >unsigned TRISA7 :1;
> >> >};
> >> >struct {
> >> >unsigned RA0 :1;
> >> >unsigned RA1 :1;
> >> >unsigned RA2 :1;
> >> >unsigned RA3 :1;
> >> >unsigned RA4 :1;
> >> >unsigned RA5 :1;
> >> >unsigned RA6 :1;
> >> >unsigned RA7 :1;
> >> >};
> >> >} TRISAbits_t;
> >> >extern volatile TRISAbits_t TRISAbits @ 0xF92;
> >> >
> >> >What is the point of making the same bits accessible through more tha=
n
> >> one
> >> >name?
> >> >
> >> >I.e. the following lines of code are identical, correct?
> >> >
> >> >TRISAbits.RA0 =3D 1;
> >> >TRISAbits.TRISA0 =3D 1;
> >> >
> >> >The LATAbits definition is even more convoluted:
> >> >
> >> >typedef union {
> >> >struct {
> >> >unsigned LATA0 :1;
> >> >unsigned LATA1 :1;
> >> >unsigned LATA2 :1;
> >> >unsigned LATA3 :1;
> >> >unsigned LATA4 :1;
> >> >unsigned LATA5 :1;
> >> >unsigned LATA6 :1;
> >> >unsigned LATA7 :1;
> >> >};
> >> >struct {
> >> >unsigned LA0 :1;
> >> >};
> >> >struct {
> >> >unsigned :1;
> >> >unsigned LA1 :1;
> >> >};
> >> >struct {
> >> >unsigned :2;
> >> >unsigned LA2 :1;
> >> >};
> >> >struct {
> >> >unsigned :3;
> >> >unsigned LA3 :1;
> >> >};
> >> >struct {
> >> >unsigned :4;
> >> >unsigned LA4 :1;
> >> >};
> >> >struct {
> >> >unsigned :5;
> >> >unsigned LA5 :1;
> >> >};
> >> >struct {
> >> >unsigned :6;
> >> >unsigned LA6 :1;
> >> >};
> >> >struct {
> >> >unsigned :7;
> >> >unsigned LA7 :1;
> >> >};
> >> >} LATAbits_t;
> >> >extern volatile LATAbits_t LATAbits @ 0xF89;
> >> >
> >> >I don't know why they union'd a separate struct for each of the bits
> >> >instead of putting them all in one struct like with TRISAbits, but th=
e
> >> same
> >> >question applies to this as well.
> >> >
> >> >What's the point of all that redundancy?
> >> >
> >> >Thanks,
> >> >
> >> >Nate
> >> >
> >> >-----
> >> >
> >> >I'm a college student, take it easy on me ;-)


--=20
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

--=20
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