t61x_watchdog.c

芯科原厂所有c8051fxx程序的例子。

//-----------------------------------------------------------------------------
// T61x_Watchdog.c
//-----------------------------------------------------------------------------
// Copyright 2007 Silicon Laboratories, Inc.
// http://www.silabs.com  
//
// Program Description:
//
// This program helps the user to learn about operating the Watch Dog Timer.
// The WDT is used to generate resets if the times between writes to the WDT 
// update register (PCA0CPH2) exceed a specified limit. The WDT can be disabled
// and enabled in the software as needed. When enabled the PCA Module 4 acts as
// the WDT. This program resets the MCU when P0.7 switch is pressed. Also upon 
// reset the LED blinks approximately five times faster when compared to before
// The reset is caused due to a WDT overflow and can be confirmed by checking 
// the value of the RSTSRC register where bit 3 is set to indicate a reset
// caused by WDT.
// 
// How to Test:
// 1) Compile and download code to a 'T61x device.
// 2) Place shorting blocks on LED/P1.0 and SW/P0.7 pin pairs on 
//    jumper J9.
// 3) Run the code:
//        - The test will blink the LED at a rate of 10Hz until the switch SW
//          (P0.7) is pressed.
//        - Once the the switch is pressed it will cause the WDT to trip and 
// 		    cause a reset.
//        - Upon reset the code checks for a WDT reset and blinks the LED five 
// 		    times faster than before to indicate the same.      
//
//
// FID:            31X000010
// Target:         C8051T61x
// Tool chain:     Keil C51 7.50 / Keil EVAL C51
// Command Line:   None
//
// Release 1.0
//    -Initial Revision SM
//    -16 AUG 2007	

//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include <compiler_defs.h>
#include <c8051T610_defs.h>            // SFR declarations

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

#define SYSCLK       24500000 / 8      // SYSCLK frequency in Hz

SBIT (LED, SFR_P1, 0);                 // LED==1 means ON
SBIT (SW, SFR_P0, 7);                 // SW==0 means switch depressed

//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void);
void PORT_Init (void);
void PCA_Init (void);
void Timer2_Init (int counts);

INTERRUPT_PROTO (TIMER2_ISR, INTERRUPT_TIMER2);

//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------
//
// The MAIN routine performs all the intialization, and then loops until the 
// switch is pressed. When SW (P0.7) is pressed the code checks the RSTSRC 
// register to make sure if the last reset is because of WDT.
//-----------------------------------------------------------------------------
void main (void) 
{
   
   // disable watchdog timer
   PCA0MD &= ~0x40;                    // WDTE = 0 (clear watchdog timer 
                                       // enable)
   // Initialize system clock to 24.5/8 MHz
   OSCILLATOR_Init ();                        
   PCA_Init();                         // Intialize the PCA
   PORT_Init();                        // Initialize crossbar and GPIO
      
   if ((RSTSRC & 0x02) == 0x00)        // First check the PORSF bit. if PORSF
   {                                   // is set, all other RSTSRC flags are
                                       // invalid
      // Check if the last reset was due to the Watch Dog Timer
      if (RSTSRC == 0x08)                   
      { 
         // Make LED blink at 50Hz
         Timer2_Init (SYSCLK / 12 / 50); 
         // Enable global interrupts
         EA = 1;                         
         while(1);                   // wait forever
      }
      else 
      {
         // Init Timer2 to generate interrupts at a 10Hz rate.
         Timer2_Init (SYSCLK / 12 / 10); 
      }                                   
   
   }
   // Calculate Watchdog Timer Timeout
   // Offset calculated in PCA clocks
   // Offset = ( 256 x PCA0CPL4 ) + 256 - PCA0L
   //        = ( 256 x 255(0xFF)) + 256 - 0
   // Time   = Offset * (12/SYSCLK)   
   //        = 255 ms ( PCA uses SYSCLK/12 as its clock source)
   
   PCA0MD  &= ~0x40;                   // WDTE = 0 (clear watchdog timer 
                                       // enable)
   PCA0L    = 0x00;                    // Set lower byte of PCA counter to 0  
   PCA0H    = 0x00;                    // Set higher byte of PCA counter to 0
   PCA0CPL4 = 0xFF;                    // Write offset for the WDT 
   PCA0MD  |= 0x40;                    // Enable the WDT
   EA = 1;                             // Enable global interrupts
   
      
   //--------------------------------------------------------------------------
   // Main Application Loop/Task Scheduler
   //--------------------------------------------------------------------------

   while (1) 
   {   
      //-----------------------------------------------------------------------
      // Task #1 - Check Port I/O
      //-----------------------------------------------------------------------
      while(!SW);                     // Force the MCU to stay in this task as
                                       // long as SW is pressed. This task 
                                       // must finish before the watchdog timer
                                       // timeout expires.

      //-----------------------------------------------------------------------
      // Task #2 - Reset Watchdog Timer
      //-----------------------------------------------------------------------
      PCA0CPH4 = 0x00;                 // Write a 'dummy' value to the PCA0CPH4 
                                       // register to reset the watchdog timer 
                                       // timeout. If a delay longer than the 
                                       // watchdog timer delay occurs between 
                                       // successive writes to this register,
                                       // the device will be reset by the watch
                                       // dog timer.                           
    }
}

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

//-----------------------------------------------------------------------------
// OSCILLATOR_Init
//-----------------------------------------------------------------------------
// Return Value : None
// Parameters   : None
// This routine initializes the system clock to use the internal 24.5MHz / 8 
// oscillator as its clock source.  Also enables missing clock detector reset.
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void)
{ 

   OSCICN = 0x80;                      // Configure internal oscillator for
                                       // its lowest frequency
   RSTSRC = 0x04;                      // Enable missing clock detector
}

//-----------------------------------------------------------------------------
// PCA_Init
//-----------------------------------------------------------------------------
// Return Value : None
// Parameters   : None
// This routine initializes the PCA to use the SYSCLK / 12 
// as its clock source.  It also sets the offset value by writing to PCA0CPL2.
//-----------------------------------------------------------------------------
void PCA_Init()
{
    PCA0CN     =  0x40;        		// PCA counter enable
    PCA0MD    &= ~0x40 ;       		// Watchdog timer disabled-clearing bit 6
    PCA0MD    &=  0xF1;        		// Timebase selected - System clock / 12
    PCA0CPL4   =  0xFF;        		// Offset value
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
// Return Value : None
// Parameters   : None
//
// This function configures the Crossbar and GPIO ports.
// P1.0   digital   push-pull     LED
//-----------------------------------------------------------------------------
void PORT_Init (void)
{

   XBR0     = 0x00;                    // No digital peripherals selected
   XBR1     = 0x40;                    // Enable crossbar and weak pull-ups
   P1MDOUT |= 0x01;                    // Enable LED as a push-pull output
}

//-----------------------------------------------------------------------------
// Timer2_Init
//-----------------------------------------------------------------------------
// Return Value : None
// Parameters   :
//   1)  int counts - calculated Timer overflow rate
//                    range is positive range of integer: 0 to 32767 
//
// Configure Timer2 to 16-bit auto-reload and generate an interrupt at 
// interval specified by <counts> using SYSCLK/48 as its time base.
//-----------------------------------------------------------------------------
void Timer2_Init (int counts)
{
   TMR2CN  = 0x00;                     // Stop Timer2; Clear TF2
                                       // use SYSCLK/12 as timebase
   CKCON  &= ~0x60;                    // Timer2 clocked based on T2XCLK

   TMR2RL  = -counts;                  // Init reload values
   TMR2    = 0xffff;                   // Set to reload immediately
   ET2     = 1;                        // Enable Timer2 interrupts
   TR2     = 1;                        // Start Timer2
}

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

//-----------------------------------------------------------------------------
// Timer2_ISR
//-----------------------------------------------------------------------------
// This routine changes the state of the LED whenever Timer2 overflows.
//-----------------------------------------------------------------------------
INTERRUPT (TIMER2_ISR, INTERRUPT_TIMER2)
{
   TF2H = 0;                           // Clear Timer2 interrupt flag
   LED = ~LED;                         // Change state of LED
}

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