timer0_poll1.c

c8051f020开发板的所有参考程序

//-----------------------------------------------------------------------------
// Timer0_Poll1.c
//-----------------------------------------------------------------------------
// Copyright 2001 Cygnal Integrated Products, Inc.
//
// AUTH: BW
// DATE: 27 AUG 01
//
// This program shows an example of using Timer0 in polled mode to implement
// a delay counter with a resolution of 1 ms.
//
// Assumes an 22.1184MHz crystal is attached between XTAL1 and  XTAL2.
// 
// The system clock frequency is stored in a global constant SYSCLK.
//
// Target: C8051F02x
// Tool chain: KEIL C51 6.03 / KEIL EVAL C51
//

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

#include <c8051f020.h>                 // SFR declarations

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

sfr16 DP       = 0x82;                 // data pointer
sfr16 TMR3RL   = 0x92;                 // Timer3 reload value
sfr16 TMR3     = 0x94;                 // Timer3 counter
sfr16 ADC0     = 0xbe;                 // ADC0 data
sfr16 ADC0GT   = 0xc4;                 // ADC0 greater than window
sfr16 ADC0LT   = 0xc6;                 // ADC0 less than window
sfr16 RCAP2    = 0xca;                 // Timer2 capture/reload
sfr16 T2       = 0xcc;                 // Timer2
sfr16 RCAP4    = 0xe4;                 // Timer4 capture/reload
sfr16 T4       = 0xf4;                 // Timer4
sfr16 DAC0     = 0xd2;                 // DAC0 data
sfr16 DAC1     = 0xd5;                 // DAC1 data

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

#define SYSCLK       22118400          // SYSCLK frequency in Hz

sbit LED = P1^6;                       // LED='1' means ON
sbit SW1 = P3^7;                       // SW1='0' means switch pressed

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

void SYSCLK_Init (void);
void PORT_Init (void);
void Timer0_Delay (int ms);

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

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

void main (void) {

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

   SYSCLK_Init ();                     // initialize oscillator
   PORT_Init ();                       // initialize crossbar and GPIO

   while (1) {
      Timer0_Delay (100);              // delay for 100ms
      LED = ~LED;                      // change state of LED
   }
}

//-----------------------------------------------------------------------------
// 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++) ;           // Wait for osc. to start up

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

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

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports
//
void PORT_Init (void)
{
   XBR0    = 0x00;
   XBR1    = 0x00;
   XBR2    = 0x40;                     // Enable crossbar and weak pull-ups
   P1MDOUT |= 0x40;                    // enable P1.6 (LED) as push-pull output
}

//-----------------------------------------------------------------------------
// Timer0_Delay
//-----------------------------------------------------------------------------
//
// Configure Timer0 to delay <ms> milliseconds before returning.
//
void Timer0_Delay (int ms)
{
   int i;                              // millisecond counter

   TCON  &= ~0x30;                     // STOP Timer0 and clear overflow flag
   TMOD  &= ~0x0f;                     // configure Timer0 to 16-bit mode
   TMOD  |=  0x01;
   CKCON |=  0x08;                     // Timer0 counts SYSCLKs

   for (i = 0; i < ms; i++) {          // count milliseconds
      TR0 = 0;                         // STOP Timer0
      TH0 = (-SYSCLK/1000) >> 8;       // set Timer0 to overflow in 1ms
      TL0 = -SYSCLK/1000;
      TR0 = 1;                         // START Timer0
      while (TF0 == 0);                // wait for overflow
      TF0 = 0;                         // clear overflow indicator
   }
}