timer.c

/////////////////////////////////////////////////////////////////////////////
// Basic HC9S12 Output Compare Timer Functionality
/////////////////////////////////////////////////////////////////////////////

#include <hidef.h>      /* common defines and macros */
#include "derivative.h" /* derivative-specific definitions */

#include "pll.h"
#include "swled.h"

/////////////////////////////////////////////////////////////////////////////
// Main Entry
/////////////////////////////////////////////////////////////////////////////
void main(void)
{
  // main entry point - these two lines must appear first
  _DISABLE_COP();
  EnableInterrupts;
  
  /////////////////////////////////////////////////////////////////////////////
  // one-time initializations
  /////////////////////////////////////////////////////////////////////////////
  PLL_To20MHz();
  (void) SWLInit();

  //Initialize Timer.  OC0
  // Turn the thing on
  TSCR1 = 0b10000000; //TSCR1_TEN is bit 7.  Turn it on. 7.3.2.6
  // Set Prescale of 128
  TSCR2 = 7; //0b00000111;  //Timer rate = BUSSPD/2^7 = 20 MHz/128 = 156.25 KHz (6.4 us tick) 
  // Use channel 0 OC
  TIOS |= 0b00000001; //1
  // Toggle the pin for channel 0 (pin 9)
  TCTL2 = 0b0000001;

  //Timer for OC0 is currently set up. Let's use it.
  // 1 - Clear any pending flags
  TFLG1 = 1; // Yes, 1 clears.  Not 0

  //Arm for an event in 100 ms
  TC0 = TCNT + 15625;// 100 ms / 6.4 us = 15625

  //Main loop
  for (;;)
  {
  // Nothing else to do right now, so just wait for the timer
    while (!TFLG1); //Spin till you see the 1 on the flag
    TFLG1 = 1; //Clear flag
    TC0 = TC0 + 15625;
    (void) SWLToggle(SWLGreen); //Toggle the green LED so I know it's working
  } 
}

/////////////////////////////////////////////////////////////////////////////
// Functions
/////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////////////////////////////////////
// Interrupt Service Routines
/////////////////////////////////////////////////////////////////////////////