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