timer.c

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/* -*- c++ -*- */
/*
 * Copyright 2003 Free Software Foundation, Inc.
 * 
 * This file is part of GNU Radio
 * 
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 * 
 * GNU Radio is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#include "timer.h"
#include "fx2regs.h"
#include "isr.h"

/*
 * Arrange to have isr_tick_handler called at 100 Hz.
 *
 * The cpu clock is running at 48e6.  The input to the timer
 * is 48e6 / 12 = 4e6.
 *
 * We arrange to have the timer overflow every 40000 clocks == 100 Hz
 */

#define	RELOAD_VALUE	((unsigned short) -40000)

void 
hook_timer_tick (unsigned short isr_tick_handler)
{
  ET2 = 0;			// disable timer 2 interrupts
  hook_sv (SV_TIMER_2, isr_tick_handler);
  
  RCAP2H = RELOAD_VALUE >> 8;	// setup the auto reload value
  RCAP2L = RELOAD_VALUE;

  T2CON = 0x04;			// interrupt on overflow; reload; run
  ET2 = 1;			// enable timer 2 interrupts
}