cryosc.c

来自「8051试验程序 基础教材」· C语言 代码 · 共 100 行

//-----------------------------------------------------------------------------
// Cryosc.c
//-----------------------------------------------------------------------------
// Copyright (C) 2005 Silicon Laboratories, Inc.
//
// AUTH: BW
// DATE: 19 JUL 01
//
// This program shows an example of configuring the external oscillator for
// use with a crystal.
//
// Assumes an 22.1184MHz crystal is attached between XTAL1 and XTAL2.
//
// Target: C8051F02x
//

//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <ioC8051f020.h>                 // SFR declarations

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F02x
//-----------------------------------------------------------------------------

__sfr __no_init volatile unsigned short DP       @ 0x82;                 // data pointer
__sfr __no_init volatile unsigned short TMR3RL   @ 0x92;                 // Timer3 reload value
__sfr __no_init volatile unsigned short TMR3     @ 0x94;                 // Timer3 counter
__sfr __no_init volatile unsigned short ADC0     @ 0xbe;                 // ADC0 data
__sfr __no_init volatile unsigned short ADC0GT   @ 0xc4;                 // ADC0 greater than window
__sfr __no_init volatile unsigned short ADC0LT   @ 0xc6;                 // ADC0 less than window
__sfr __no_init volatile unsigned short RCAP2    @ 0xca;                 // Timer2 capture/reload
__sfr __no_init volatile unsigned short T2       @ 0xcc;                 // Timer2
__sfr __no_init volatile unsigned short RCAP4    @ 0xe4;                 // Timer4 capture/reload
__sfr __no_init volatile unsigned short T4       @ 0xf4;                 // Timer4
__sfr __no_init volatile unsigned short DAC0     @ 0xd2;                 // DAC0 data
__sfr __no_init volatile unsigned short DAC1     @ 0xd5;                 // DAC1 data

//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------

#define SYSCLK       22118400          // SYSCLK frequency in Hz

#define LED P1_bit.P16                       // LED='1' means ON
#define SW1 P3_bit.P37                       // SW1='0' means switch pressed

//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------

void SYSCLK_Init (void);

//-----------------------------------------------------------------------------
// Global VARIABLES
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------

void main (void) {

   WDTCN = 0xde;                       // disable watchdog timer
   WDTCN = 0xad;

   SYSCLK_Init ();                     // initialize oscillator

   while (1);
}

//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// This routine initializes the system clock to use an 22.1184MHz crystal
// as its clock source.
//
void SYSCLK_Init (void)
{
   int i;                              // delay counter

   OSCXCN = 0x67;                      // start external oscillator with
                                       // 22.1184MHz crystal

   for (i=0; i < 256; i++) ;           // XTLVLD blanking interval (>1ms)

   while (!(OSCXCN & 0x80)) ;          // Wait for crystal osc. to settle

   OSCICN = 0x88;                      // select external oscillator as SYSCLK
                                       // source and enable missing clock
                                       // detector
}