>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:


----

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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 way.
>
> 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 fo=
r
> >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 than o=
ne
> >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 the
> 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 ;-)
> >
> >Check out my small hobby electronics business!
> >www.foxytronics.com
> >--
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>
>
> --
> 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
>
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