www.pudn.com > Watchdog.rar > F32x_Watchdog.c, change:2007-09-12,size:10869b


//----------------------------------------------------------------------------- 
// F32x_Watchdog.c 
//----------------------------------------------------------------------------- 
// Copyright 2006 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 P2.0 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 'F32x device. 
// 2) Run the code: 
//        - The test will blink the LED at a rate of 10Hz until the switch SW2 
//          (P2.0) is pressed. 
//        - Once the the switch is pressed and held for a long enough time,  
//          it will prevent the WDT from being touched and the WDT will 
// 		    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:            32X000080 
// Target:         C8051F032x 
// Tool chain:     Keil C51 7.50 / Keil EVAL C51 
// Command Line:   None 
// 
// Release 1.0 
//    -Initial Revision SM 
//    -15 JULY 2006	 
 
//----------------------------------------------------------------------------- 
// Includes 
//----------------------------------------------------------------------------- 
#include <c8051f320.h>                 // SFR declarations 
 
//----------------------------------------------------------------------------- 
// 16-bit SFR Definitions for 'F32x 
//----------------------------------------------------------------------------- 
 
sfr16 TMR2RL   = 0xca;                 // Timer2 reload value 
sfr16 TMR2     = 0xcc;                 // Timer2 counter 
 
//----------------------------------------------------------------------------- 
// Global CONSTANTS 
//----------------------------------------------------------------------------- 
 
#define SYSCLK       24500000 / 8      // SYSCLK frequency in Hz 
 
sbit LED = P2^2;                       // LED='1' means ON 
sbit SW2 = P2^0;                       // SW2='0' means switch pressed 
 
//----------------------------------------------------------------------------- 
// Function PROTOTYPES 
//----------------------------------------------------------------------------- 
 
void OSCILLATOR_Init (void); 
void PORT_Init (void); 
void PCA_Init (void); 
void Timer2_Init (int counts); 
void Timer2_ISR (void); 
 
//----------------------------------------------------------------------------- 
// main() Routine 
//----------------------------------------------------------------------------- 
// 
// The MAIN routine performs all the intialization, and then loops until the  
// switch is pressed. When SW2 (P2.0) 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)                    	 
   	{  
	   	Timer2_Init (SYSCLK / 12 / 50);  
	   	// Make LED blink at 50Hz 
       	EA = 1;                          
	   	// Enable global interrupts 
	   	while(1);                   // wait forever 
   	}	 
   	else  
   	{ 
	   	Timer2_Init (SYSCLK / 12 / 10);  
	   	// Init Timer2 to generate interrupts at a 10Hz rate. 
	   }                                    
    
   } 
    // 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(!SW2);					// Force the MCU to stay in this task as  
						   			// long as SW2 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. 
// P2.2   digital   push-pull     LED 
//----------------------------------------------------------------------------- 
void PORT_Init (void) 
{ 
 
   XBR0     = 0x00;                    // no digital peripherals selected 
   XBR1     = 0x40;                    // Enable crossbar and weak pull-ups 
   P2MDOUT |= 0x04;                    // 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  &= ~0x30;                       // 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. 
//----------------------------------------------------------------------------- 
void Timer2_ISR (void) interrupt 5 
{ 
   TF2H = 0;                           // clear Timer2 interrupt flag 
   LED = ~LED;                         // change state of LED 
} 
 
//----------------------------------------------------------------------------- 
// End Of File 
//-----------------------------------------------------------------------------