f500_comparator0_resetsource.c

C8051F500开发编程：MCU全部资源应用实例

//-----------------------------------------------------------------------------
// F500_Comparator0_ResetSource.c
//-----------------------------------------------------------------------------
// Copyright 2008 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// Silicon Laboratories MCUs can use different mechanisms to reset the device.
//
// This software shows the necessary configuration to use Comparator0 as
// a reset source.  The code executes the initialization routines and then
// spins in an infinite while() loop.  If the button on P1.4 (on the target
// board) is pressed, then the comparators postive input (CP0+) input will drop
// below the comparator's negative input (CP0-).  When this happens,
// Comparator0 will cause the device to be reset.
//
// When the code is waiting for the button to be pressed, the LED is on.
//
// Upon every device reset, the code checks the RSTSRC register to determine
// if the last reset was due to a comparator reset.  If it was a
// comparator reset, the code will blink the LED constantly.
//
// How To Test:
//
// 1) Compile and download code to a 'F500 target board
// 2) On the target board, connect P0.0 to P1.4 and P0.1 to P1.3
// 3) Verify that the P1.4 - SW shorting block is in place on J19
// 4) Run the code and verify that the LED is on
// 5) Press the P1.4 switch (this causes a comparator reset)
// 6) Verify that the LED is blinking
//
//
// Target:         C8051F500 (Side A of a C8051F500-TB)
// Tool chain:     Keil C51 8.0 / Keil EVAL C51
// Command Line:   None
//
// Release 1.1 / 10 JUN 2008 (ADT)
//    -Edited formatting
//
// Release 1.0 / 03 MAR 2008 (GP)
//    -Initial Revision
//

//-----------------------------------------------------------------------------
// Include Files
//-----------------------------------------------------------------------------

#include <compiler_defs.h>
#include <C8051F500_defs.h>            // SFR declarations

//-----------------------------------------------------------------------------
// Global Constants
//-----------------------------------------------------------------------------

#define SYSCLK             24000000    // Clock speed in Hz
#define COMPARATOR_SETTLE        10    // Settle time in us

SBIT (LED, SFR_P1, 3);                 // LED == 1 means ON
SBIT (SW1, SFR_P1, 4);                 // SW1 == 0 means switch depressed

//-----------------------------------------------------------------------------
// Function Prototypes
//-----------------------------------------------------------------------------

void OSCILLATOR_Init (void);           // Configure the system clock
void PORT_Init (void);                 // Configure the Crossbar and GPIO
void COMPARATOR0_Init (void);          // Configure Comparator0
void ResetSRC_Init (void);             // Configure Reset Sources

void TIMER0_Delay (U16 us);            // Used as a delay

//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------
void main (void)
{
   SFRPAGE = ACTIVE_PAGE;              // Set SFR Page for PCA0MD and RSTSRC

   PCA0MD &= ~0x40;                    // Disable the watchdog timer

   OSCILLATOR_Init ();                 // Initialize the system clock
   PORT_Init ();                       // Initialize crossbar and GPIO
   COMPARATOR0_Init ();                // Initialize Comparator0

   // When checking the RSTSRC register for the source of the last reset,
   // you must first also check that the PORSF bit is also '0'.  If the PORSF
   // bit is set ('1'), then all other bits in the RSTSRC register are invalid.

   // If last reset was due to comparator reset
   if (((RSTSRC & 0x02) == 0x00) && ((RSTSRC & 0x20) == 0x20))
   {
      while (1)
      {
         TIMER0_Delay (30000);         // Delay
         LED = ~LED;                   // Flip LED state
      }
   }
   // Last reset was due to a power-on reset or something else
   else
   {
      ResetSRC_Init ();                // Init comparators as reset source
      LED = 1;                         // Turn LED on

      while (1);                       // Infinite while loop waiting for
                                       // comparator reset
   }
}

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

//-----------------------------------------------------------------------------
// OSCILLATOR_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This routine initializes the system clock to use the precision internal
// oscillator as its clock source.
//-----------------------------------------------------------------------------

void OSCILLATOR_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = CONFIG_PAGE;

   OSCICN = 0x84;                      // Configure internal oscillator for
                                       // 24 MHz / 8

   SFRPAGE = ACTIVE_PAGE;

   RSTSRC = 0x04;                      // Enable missing clock detector

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the crossbar and GPIO ports.
//
// P0.0   digital   open-drain    Comparator + Input
// P0.1   digital   open-drain    Comparator - Input
// P1.3   digital   push-pull     LED
// P1.4   digital   open-drain    Switch
//-----------------------------------------------------------------------------

void PORT_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = CONFIG_PAGE;

   P0SKIP   = 0x03;                    // Skip P0.0 and P0.1 in
                                       // crossbar assignment

   P0MDIN  &= ~0x03;                   // Comparator 0 inputs (P0.0 and P0.1)
                                       // are analog inputs.
   P1MDOUT  = 0x08;                    // LED is push-pull output

   XBR2     = 0x40;                    // Enable crossbar and weak pull-ups

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// COMPARATOR0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the comparator to pins P0.0 and P0.1
//-----------------------------------------------------------------------------

void COMPARATOR0_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = ACTIVE_PAGE;

   CPT0CN = 0x80;                      // Comparator enabled
   CPT0MX = 0x00;                      // P0.1 = Negative Input
                                       // P0.0 = Positive Input

   TIMER0_Delay (COMPARATOR_SETTLE);   // Allow CP0 output to settle for 10 us

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// ResetSRC_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the comparator as a reset source
//-----------------------------------------------------------------------------

void ResetSRC_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = ACTIVE_PAGE;

   RSTSRC = 0x20;                      // Comparator 0 -> reset source

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// TIMER0_Delay
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   :
//   1) unsigned int us - number of microseconds of delay
//                        range is full range of integer: 0 to 65335
//
// Configure Timer0 to delay <us> microseconds before returning.
//-----------------------------------------------------------------------------

void TIMER0_Delay (U16 us)
{
   U16 i;                              // Millisecond counter

   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = ACTIVE_PAGE;

   TCON  &= ~0x30;                     // STOP Timer0 and clear overflow flag
   TMOD  &= ~0x0f;                     // Configure Timer0 to 16-bit mode
   TMOD  |=  0x01;
   CKCON |=  0x04;                     // Timer0 counts SYSCLKs

   for (i = 0; i < us; i++)            // Count microseconds
   {
      TCON &= ~0x10;                   // STOP Timer0
      TH0 = (-SYSCLK / 1000000) >> 8;  // Set Timer0 to overflow in 1us
      TL0 = -SYSCLK / 1000000;
      TCON |= 0x10;                    // START Timer0
      while (TF0 == 0);                // Wait for overflow
      TCON &= ~0x20;                   // Clear overflow indicator
   }

   SFRPAGE = SFRPAGE_save;
}

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