firmware/target/arm/tcc77x/kernel-tcc77x.c

   1 /***************************************************************************
   2 *             __________               __   ___.
   3 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
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   7 *                     \/            \/     \/    \/            \/
   8 * $Id$
   9 *
  10 * Copyright (C) 2008 by Rob Purchase
  11 *
  12 * This program is free software; you can redistribute it and/or
  13 * modify it under the terms of the GNU General Public License
  14 * as published by the Free Software Foundation; either version 2
  15 * of the License, or (at your option) any later version.
  16 *
  17 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18 * KIND, either express or implied.
  19 *
  20 ****************************************************************************/
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "kernel.h"
  25 #include "timer.h"
  26 #include "thread.h"
  27
  28 void tick_start(unsigned int interval_in_ms)
  29 {
  30     /* configure Timer T-Clock to 2Mhz (clock source 4 (Xin) divided by 6) */
  31     PCLKCFG4 = (1 << 31) | (4 << 28) | (5 << 16);
  32
  33     /* disable Timer0 */
  34     TCFG0 &= ~1;
  35
  36     /* set counter reference value based on 1Mhz tick */
  37     TREF0 = interval_in_ms * 1000;
  38
  39     /* Timer0 = reset to 0, divide=2, IRQ enable, enable (continuous) */
  40     TCFG0 = (1<<8) | (0<<4) | (1<<3) | 1;
  41
  42     /* Unmask timer IRQ */
  43     IEN |= TIMER0_IRQ_MASK;
  44 }
  45
  46 /* NB: Since we are using a single timer IRQ, tick tasks are dispatched as
  47        part of the central timer IRQ processing in timer-tcc77x.c */