----- Ursprüngliche Nachricht -----
Von: Mark Rages
Gesendet am: 17 Nov 2009 22:32:59
> Before I implement my own routine, is there a standard busyloop delay
> routine for mspgcc?
Besides simple busy-loop functions (there is one in the mspgcc library), I have
implemented a fairly accurate delay function which can delay up to 65536
microseconds with high accuracy.
I use the Timer A (on the 54xx Timer1_A1) for a 1ms interrupt, running the
timer at 1MHz.
So my delay function is using the CC1 (CC0 is used for the 1ms tick).
Note:
- Calling overhead is additional 4-5...@16mhz MCLK, more on slower processors.
- GIE will be enabled while waiting
- any other IRQ happening immediately after or shortly before the timer has run
out will add to the delay.
- any other IRQ happening while waiting will NOT add to the delay.
volatile char usdelay;
void TimerDelay1us(unsigned int time){
__asm__ __volatile__ ( "push r2"::);
// save interrupt state
_DINT();
// disable interrupt (to allow proper setup)
usdelay=1;
TA1CCR2=TA1R+time+2;
TA1CCTL2=CCIE;
_EINT();
// enable interrupt (to allow CCI take place)
while(usdelay);
TA1CCTL2=0;
__asm__ __volatile__ ( "pop r2"::);
// restore original interrupt state
}
interrupt(TIMER1_A1_VECTOR) timera1x_handler(void){
__asm__ __volatile__("add %[src] ,r0 ":: [src] "m" (TA1IV));
__asm__ __volatile__("reti "::); // NO INT
__asm__ __volatile__("jmp timera1_cc1_handler "::); // CC1
__asm__ __volatile__("jmp timera1_cc2_handler "::); // CC2
__asm__ __volatile__("reti "::); // RESERVED
__asm__ __volatile__("reti "::); // RESERVED
__asm__ __volatile__("reti "::); // RESERVED
__asm__ __volatile__("reti "::); // RESERVED
__asm__ __volatile__("jmp timera1_ifg_handler "::); // IFG
}
interrupt(NOVECTOR) timera1_cc1_handler(void){} // currently unused
interrupt(NOVECTOR) timera1_cc2_handler(void){ // TACC2 used for µs timer delay
usdelay=0;
}
interrupt(NOVECTOR) timera1_ifg_handler(void){}
Of course this is a LOT of effort if you don't need any precision. But if you
do, it's far better than any variable-decrementing busy-loop and has a wide
operating range of up to 65 milliseconds.
JMGross
