f31x_timer0_8bitreloadtimer.c

C8051F31系列单片机的例子

//-----------------------------------------------------------------------------
// F31x_Timer0_8bitReloadTimer.c
//-----------------------------------------------------------------------------
// Copyright 2005 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// This program presents an example of use of the Timer0 of the C8051F31x's in
// 8-bit counter/timer with reload mode. It uses the 'F310DK as HW platform.
// It uses the Timer0 to create an interrupt at a certain rate and when the
// user's interrupt counter reaches the selected value the LED is toggled.
//
//
// Pinout:
//
//    P3.3 -> LED
//
//    all other port pins unused
//
// How To Test:
//
// 1) Load the F31x_Timer0_8bitReloadTimer.c file in the Silicon Labs IDE.
// 2) If a different LED blink rate is required change the following constant:
//       -> LED_TOGGLE_RATE in milliseconds
// 3) Compile and download code to a 'F31x device
// 4) Verify the LED pins of J3 are populated on the 'F31x TB.
// 5) Run the code
// 6) Check the toggling of the LED (P3.3)
//
//
// FID:            31X000028
// Target:         C8051F31x
// Tool chain:     KEIL C51 7.20 / KEIL EVAL C51
// Command Line:   None
//
// Release 1.0
//    -Initial Revision (CG)
//    -5 Dec. 2005
//
// Note: All time estimates are for SYSCLK freq ~ 24.5MHz
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <C8051F310.h>                 // SFR declarations

//-----------------------------------------------------------------------------
// Global Constants
//-----------------------------------------------------------------------------

#define SYSCLK             24500000/8  // SYSCLK in Hz (24.5 MHz internal
                                       // oscillator / 8)
                                       // the internal oscillator has a
                                       // tolerance of +/- 2%

#define TIMER_PRESCALER            48  // Based on Timer CKCON settings

// There are SYSCLK/TIMER_PRESCALER timer ticks per second, so
// SYSCLK/TIMER_PRESCALER/1000 timer ticks per millisecond.
#define TIMER_TICKS_PER_MS  SYSCLK/TIMER_PRESCALER/1000

// Note: TIMER_TICKS_PER_MS should not exceed 255 (0xFF) for the 8-bit timer

#define AUX1     TIMER_TICKS_PER_MS
#define AUX2     -AUX1

#define LED_TOGGLE_RATE           2000  // LED toggle rate in milliseconds
                                       // if LED_TOGGLE_RATE = 1, the LED will
                                       // be on for 1 millisecond and off for
                                       // 1 millisecond

#define TIMER0_RELOAD_HIGH       AUX2  // Reload value for Timer0 high byte

sbit LED = P3^3;                       // LED

//-----------------------------------------------------------------------------
// Function Prototypes
//-----------------------------------------------------------------------------

void Port_Init (void);                 // Port initialization routine
void Timer0_Init (void);               // Timer0 initialization routine

//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------

void main (void)
{
   PCA0MD &= ~0x40;                    // WDTE = 0 (clear watchdog timer
                                       // enable)
   Timer0_Init ();                     // Initialize the Timer0
   Port_Init ();                       // Init Ports
   EA = 1;                             // Enable global interrupts

   while (1);                          // Loop forever
}

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

//-----------------------------------------------------------------------------
// Port_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the crossbar and GPIO ports.
//
// Pinout:
//
//    P3.3 -> LED
//
//    all other port pins unused
//
//-----------------------------------------------------------------------------
void Port_Init (void)
{
   XBR1 = 0x40;                        // Enable crossbar
   P3MDOUT = 0x08;                     // Set LED
}

//-----------------------------------------------------------------------------
// Timer0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the Timer0 as a 8-bit timer with reload, interrupt
// enabled.
// Using the internal osc. at 24.5MHz with a prescaler of 1:8 and reloading
// TL0 register with TH0 it will interrupt aproximately one time every 1msec.
//
// Note: The Timer0 uses a 1:48 prescaler.  If this setting changes, the
// TIMER_PRESCALER constant must also be changed.
//-----------------------------------------------------------------------------
void Timer0_Init(void)
{
   TH0 = TIMER0_RELOAD_HIGH;           // Init Timer0 High register
   TL0 = TH0;                          // Set the intial Timer0 value

   TMOD = 0x02;                        // Timer0 in 8-bit reload mode
   CKCON = 0x02;                       // Timer0 uses a 1:48 prescaler
   ET0=1;                              // Timer0 interrupt enabled
   TCON = 0x10;                        // Timer0 ON
}


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

//-----------------------------------------------------------------------------
// Timer0_ISR
//-----------------------------------------------------------------------------
//
// Here we process the Timer0 interrupt and toggle the LED when appropriate
//
//-----------------------------------------------------------------------------
void Timer0_ISR (void) interrupt 1
{
   static int counter = 0;

   if((counter++) == LED_TOGGLE_RATE)
   {
      LED = ~LED;                      // Toggle the LED
      counter = 0;
   }
}

//-----------------------------------------------------------------------------
// End Of File
//-----------------------------------------------------------------------------