[avr-libc-dev] cannot access TCC0.PER or any other 16-bit register on ATXMega128A1

[Stefan Schoenleitner]

Hi,

I'm trying to set up a timer on an ATXMega128A1 using avr-gcc 4.3.4 
and avr-libc 1:1.6.7-1ubuntu2.

In my code I have the following:

------------------------------
#include <avr/io.h>
.....

TCC0.CTRLD = TC_EVACT_QDEC_gc | TC_EVSEL_CH0_gc;
TCC0.PER = 1000;
TCC0.CTRLA = TC_CLKSEL_DIV1_gc;
------------------------------

However, when compiling I get the following error:
------------------------------
$ avr-gcc -Os -gstabs -std=c99 -funsigned-char -funsigned-bitfields 
-fpack-struct -fshort-enums -Wall -Wstrict-prototypes -pedantic 
-mmcu=atxmega128a1 -c -o main.o main.c
main.c: In function ‘main’:
main.c:130: error: ‘TC0_t’ has no member named ‘PER’
make: *** [main.o] Error 1
------------------------------


I had a closer look at avr/iox128a1.h and saw that in contrast to
the compiler error, there is a PER register defined:

------------------------------
#define TCC0    (*(TC0_t *) 0x0800)  /* Timer/Counter C0 */
...
#define TCC0_PER  _SFR_MEM16(0x0826)
....
typedef struct TC0_struct
{
    register8_t CTRLA;  /* Control  Register A */
    ...
    _WORDREGISTER(PER);  /* Period */
    ...
} TC0_t;
------------------------------


Since "PER" is definitely in the struct, I'm really wondering why I get the 
compiler error above.
I suppose this is a bug.

A workaround is to use TCC0_PER to directly access the register.

cheers,
Stefan