//-----------------------------------------------------------------------------
// F31x_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 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 'F31x device.
// 2) Run the code:
//        - The test will blink the LED at a rate of 10Hz until the switch SW2
//          (P0.7) 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:            31X000010
// Target:         C8051F031x
// Tool chain:     Keil C51 7.50 / Keil EVAL C51
// Command Line:   None
//
// Release 1.0
//    -Initial Revision SM
//    -15 JULY 2006	

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

#include <c8051f310.h>                    // SFR declarations

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F31x
//-----------------------------------------------------------------------------

sfr16 TMR2RL   = 0xca;                 // Timer2 reload value
sfr16 TMR2     = 0xcc;                 // Timer2 counter

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

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

sbit LED = P3^3;                       // LED='1' means ON
sbit SW2 = P0^7;                       // 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 (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)                    	
   	{ 
	   	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.
// P3.3   digital   push-pull     LED
//-----------------------------------------------------------------------------
void PORT_Init (void)
{

   XBR0     = 0x00;                    // no digital peripherals selected
   XBR1     = 0x40;                    // Enable crossbar and weak pull-ups
   P3MDOUT |= 0x08;                    // 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.
//-----------------------------------------------------------------------------
void Timer2_ISR (void) interrupt 5
{
   TF2H = 0;                           // clear Timer2 interrupt flag
   LED = ~LED;                         // change state of LED
}

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