f36x_watchdog.c

芯科原厂所有c8051fxx程序的例子。

//-----------------------------------------------------------------------------
// F36x_Watchdog.c
//-----------------------------------------------------------------------------
// Copyright 2006 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// The Watchdog Timer (WDT) is a hardware timer enabled on every reset that
// will timeout after a programmable interval.  When the WDT times out, it
// will force a device reset. To prevent the reset, the WDT must be restarted
// by application software before it overflows. If the system experiences a
// software or hardware malfunction preventing the software from restarting
// the WDT, the WDT will overflow and cause a reset, returning the MCU to a
// known state.
//
// This example demonstrates how to initialize and reset the Watchdog Timer
// (using a timer) and check for a Watchdog Timer reset.
//
// How to Test:
// 1) Compile and download code to a 'F360 device.
// 2) Run the code:
//        - The test will blink the LED at a rate of 10Hz until the switch SW1
//          (P3.0) 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.
//
// FID:            36X000041
// Target:         C8051F36x
// Tool chain:     Keil C51 8.0 / Keil EVAL C51
// Command Line:   None
//
// Release 1.0
//    -Initial Revision (SM / TP)
//    -13 OCT 2006

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

#include <C8051F360.h>                 // SFR declarations

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F36x
//-----------------------------------------------------------------------------

sfr16 TMR2RL   = 0xCA;                 // Timer2 reload value
sfr16 TMR2     = 0xCC;                 // Timer2 counter

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

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

sbit LED = P3^2;                       // LED='1' means ON
sbit SW1 = P3^0;                       // SW1='0' means switch pressed

//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------

void Oscillator_Init (void);
void Port_Init (void);
void Watchdog_Init (void);
void Timer0_Init (void);
void Timer2_Init (unsigned int counts);

void Timer0_ISR (void);
void Timer2_ISR (void);

//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------
//
// The MAIN routine performs all the intialization, and then loops until the
// switch is pressed. When SW1 (P3.0) is pressed the code checks the RSTSRC
// register to make sure if the last reset is because of WDT.
//-----------------------------------------------------------------------------
void main (void)
{
   PCA0MD &= ~0x40;                    // WDTE = 0 (clear watchdog timer
                                       // enable)

   Oscillator_Init();                  // Initialize system clock to 24.5/8 MHz
   Watchdog_Init();                    // Intialize the Watchdog Timer
   Port_Init();                        // Initialize crossbar and GPIO
   Timer0_Init();                      // Initialize Timer0 to "kick" the WDT

   EA = 1;                             // Enable global interrupts

   if ((RSTSRC & 0x02) == 0x00)        // First check the PORSF bit. If PORSF
   {                                   // is set, all other RSTSRC flags are
                                       // invalid

      if (RSTSRC == 0x08)              // Check if the last reset was due to a
      {                                // WDT.
         PCA0MD &= ~0x40;              // Disable the WDT until the next reset

         // Make LED blink at 50Hz
         Timer2_Init (SYSCLK / 12 / 50);

         while (SW1 != 0);             // Wait until SW1 is pressed to reset
                                       // the WDT

         while (SW1 == 0);             // Wait until the switch is released
                                       // before continuing

         RSTSRC = 0x10;                // Force a SW reset to reset the WDT
      }
      else
      {
         // Init Timer2 to generate interrupts at a 10Hz rate.
         Timer2_Init (SYSCLK / 12 / 10);
      }
   }

   SFRPAGE = LEGACY_PAGE;

   while (1)
   {
      if (SW1 == 0)                    // If the switch (SW) is pressed, stop
      {                                // resetting the WDT, causing a reset
         TR0 = 0;

         while(1);
      }
   }
}

//-----------------------------------------------------------------------------
// 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)
{
   unsigned char SFRPAGE_save = SFRPAGE; // Save the current SFRPAGE

   SFRPAGE = CONFIG_PAGE;              // Switch to the necessary SFRPAGE

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

   SFRPAGE = SFRPAGE_save;             // Restore the SFRPAGE
}

//-----------------------------------------------------------------------------
// Watchdog_Init
//-----------------------------------------------------------------------------
// Return Value : None
// Parameters   : None
//
// This routine initializes the Watchdog timer (WDT) to use the SYSCLK / 12
// as its clock source.  It also sets the offset value by writing to PCA0CPL5.
//-----------------------------------------------------------------------------
void Watchdog_Init()
{
   unsigned char SFRPAGE_save = SFRPAGE; // Save the current SFRPAGE

   SFRPAGE = CONFIG_PAGE;              // Switch to the necessary SFRPAGE

   // Step 1: Disable the WDT by writing a