Hello,
I wanted to use the _BV macro to set the JTD bit in MCUCR in order to
disable the JTAG interface and
allow the PF4-PF7 pins for other use.
The listing result is this:
MCUCR |= _BV(JTD); // needs to be done twice
9cf2: 85 b7 in r24, 0x35 ; 53
9cf4: 80 68 ori r24, 0x80 ; 128
9cf6: 85 bf out 0x35, r24 ; 53
MCUCR |= _BV(JTD);
9cf8: 85 b7 in r24, 0x35 ; 53
9cfa: 80 68 ori r24, 0x80 ; 128
9cfc: 85 bf out 0x35, r24 ; 53
As you can see the instruction is xoring a temporary value instead of
using the expected sbi.
On the other hand if I use the same approach for a normal port
register I get the desired result:
DDRF |= _BV(PF4);
2d66: 84 9a sbi 0x10, 4 ; 16
PORTF |= _BV(PF4);
2d68: 8c 9a sbi 0x11, 4 ; 17
Any ideas why _BV works for a port register but not for MCUCR?
I'm using AT90USB1287, avr-gcc 4.5.2.
Thanks,
Omar
_______________________________________________
AVR-GCC-list mailing list
AVR-GCC-list@nongnu.org
https://lists.nongnu.org/mailman/listinfo/avr-gcc-list
