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/*
* Copyright (C) 2014 INRIA
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu
* @{
*
* @file hwtimer_msp430_.c
* @brief MSP430x16xx timer functions
*
* @author Oliver Hahm <oliver.hahm@inria.fr>
* @author Milan Babel <babel@inf.fu-berlin.de>
* @author Kévin Roussel <Kevin.Roussel@inria.fr>
*
* @}
*/
#include "cpu.h"
#include "hwtimer.h"
#include "arch/hwtimer_arch.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
extern void (*int_handler)(int);
extern void timer_unset(short timer);
extern volatile uint16_t overflow_interrupt[HWTIMER_MAXTIMERS+1];
extern volatile uint16_t timer_round;
void timerA_init(void)
{
volatile unsigned int *ccr;
volatile unsigned int *ctl;
timer_round = 0; /* Set to round 0 */
TACTL = TASSEL_1 + TACLR; /* Clear the timer counter, set ACLK */
TACTL &= ~TAIFG; /* Clear the IFG */
TACTL |= TAIE; /* Enable TAIE (overflow IRQ) */
for (int i = 0; i < HWTIMER_MAXTIMERS; i++) {
ccr = &TACCR0 + (i);
ctl = &TACCTL0 + (i);
*ccr = 0;
*ctl &= ~(CCIFG);
*ctl &= ~(CCIE);
}
TACTL |= MC_2;
}
interrupt(TIMERA0_VECTOR) __attribute__((naked)) timer_isr_ccr0(void)
{
__enter_isr();
if (overflow_interrupt[0] == timer_round) {
timer_unset(0);
int_handler(0);
}
__exit_isr();
}
interrupt(TIMERA1_VECTOR) __attribute__((naked)) timer_isr(void)
{
__enter_isr();
short taiv_reg = TAIV;
if (taiv_reg == 0x0A) {
/* TAIV = 0x0A means overflow */
DEBUG("Overflow\n");
timer_round++;
}
else {
short timer = taiv_reg >> 1;
/* check which CCR has been hit and if the overflow counter
for this timer has been reached (or exceeded);
there is indeed a race condition where an hwtimer
due to fire in the next round can be set after
the timer's counter has overflowed but *before*
timer_round incrementation has occured (when
interrupts are disabled for any reason), thus
effectively setting the timer one round in the past! */
int16_t round_delta = overflow_interrupt[timer] - timer_round;
/* in order to correctly handle timer_round overflow,
we must fire the timer when, for example,
timer_round == 0 and overflow_interrupt[timer] == 65535;
to that end, we compute the difference between the two
on a 16-bit signed integer: any difference >= +32768 will
thus overload to a negative number; we should then
correctly fire "overdue" timers whenever the case */
if (round_delta <= 0) {
timer_unset(timer);
int_handler(timer);
}
}
__exit_isr();
}