f53xa_watchdog.c

C8051F52xA_53xA型单片机看门狗驱动源代码

//-----------------------------------------------------------------------------
// F53xA_Watchdog.c
//-----------------------------------------------------------------------------
// Copyright 2007 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// This program helps the user to learn about operating the Watchdog 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 2 acts as
// the WDT. This program resets the MCU when P1.4 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.
//
// Pinout:
//
// P1.3 - LED
// P1.4 - Switch
//
//
// How to Test:
// 1) Compile and download code to a 'F53xA device (either device A or device B
//    on the target board).
// 2) Place shorting blocks on P1.3/P1.3_LED_A and P1.4/P1.4_SW pin pairs (HDR4
//    for device A or HDR3 for device B).
// 3) Run the code:
//        - The test will blink the LED at a rate of 10Hz until the switch SW
//          (P1.4) is pressed.
//        - Press and hold the switch to 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.
//
// Target:         C8051F52xA/F53xA (C8051F530A TB)
// Tool chain:     Keil C51 8.0 / Keil EVAL C51
// Command Line:   None
//
// Release 1.1
//    -Updated for 'F530A TB (TP)
//    -31 JAN 2008
//
// Release 1.0
//    -Initial Revision (SM)
//    -10 JULY 2007

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

#include "compiler_defs.h"
#include "C8051F520A_defs.h"

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

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

SBIT (LED, SFR_P1, 3);                 // LED='1' means ON
SBIT (SW, SFR_P1, 4);                  // SW='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 SW (P1.4) is pressed the code checks the RSTSRC
// register to make sure if the last reset is because of the Watchdog Timer.
//-----------------------------------------------------------------------------
void main (void)
{
   PCA0MD &= ~0x40;                    // Disable watchdog timer

   OSCILLATOR_Init ();                 // Initialize the system clock
   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 Watchdog Timer
      if (RSTSRC == 0x08)
      {
         Timer2_Init (SYSCLK / 12 / 50); // Make LED blink at 50Hz

         EA = 1;                       // Enable global interrupts
         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 PCA0CPL2 ) + 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
   PCA0CPL2 = 0x0F;                    // 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 SW2 is pressed. This task
                                       // must finish before the watchdog timer
                                       // timeout expires.

      //-----------------------------------------------------------------------
      // Task #2 - Reset Watchdog Timer
      //-----------------------------------------------------------------------
      PCA0CPH2 = 0x00;                 // Write a 'dummy' value to the PCA0CPH2
                                       // 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 = 0x84;                      // Configure internal oscillator for
                                       // 24.5 MHz / 8
   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
   PCA0MD &=  0xF1;                    // Timebase selected - System clock / 12
   PCA0CPL2 =  0xFF;                   // Offset value
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the Crossbar and GPIO ports.
//
// P1.3   digital   push-pull     LED
// P1.3   digital   open-drain    Switch (SW)
//
//-----------------------------------------------------------------------------
void PORT_Init (void)
{
   P1MDOUT |= 0x08;                    // Enable LED as a push-pull output

   XBR1 = 0x40;                        // Enable crossbar and weak pull-ups
}

//-----------------------------------------------------------------------------
// 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
//-----------------------------------------------------------------------------