I assume this is an 8 bit part, I haven't seen quite so much redundancy
on the 16/32 bit parts.

My guess is that it has to do with compatibility with other compilers.
Microchip has had relationships with a number of compiler vendors over
the years, tho they now seem to have settled on an 8 bit standard.  The
16/32 bit compilers have always been gcc, so you don't see all that
history.

Sometimes compiler and assembler developers have a "better idea" and
feel like they can somehow improve things by, for example,
calling .TRISA7 .RA7 instead.  Since Microchip supported a number of
these compilers over the years, I suspect they feel obligated to make an
attempt at retaining some degree of source compatibility.

Just my guess

--McD

On Mon, 2015-04-20 at 13:59 -0400, Nathan House wrote:
> Hi,
>=20
> The main.pre file in my MPLAB X project seems to show the definitions for
> the configuration registers. One example is this:
>=20
> 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;
>=20
> What is the point of making the same bits accessible through more than on=
e
> name?
>=20
> I.e. the following lines of code are identical, correct?
>=20
> TRISAbits.RA0 =3D 1;
> TRISAbits.TRISA0 =3D 1;
>=20
> The LATAbits definition is even more convoluted:
>=20
> 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;
>=20
> 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 sa=
me
> question applies to this as well.
>=20
> What's the point of all that redundancy?
>=20
> Thanks,
>=20
> Nate
>=20
> -----
>=20
> I'm a college student, take it easy on me ;-)
>=20
> Check out my small hobby electronics business!
> www.foxytronics.com


--=20
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