f93x_oscillator_spreadspectrum.c

芯科原厂所有c8051fxx程序的例子。

//-----------------------------------------------------------------------------
// F93x_Oscillator_SpreadSpectrum.c
//-----------------------------------------------------------------------------
// Copyright 2007 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// This program demonstrates how to configure the system clock to use the 
// precision internal oscillator with spread spectrum mode enabled.
//
//
// How To Test:
//
// 1) Download code to an 'F93x target board.
// 2) Measure the frequency output on P0.0.
//
//
// Target:         C8051F93x-C8051F92x
// Tool chain:     Generic
// Command Line:   None
//
// Release 1.0
//    -Initial Revision (FB)
//    -15 AUG 2007
//

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

#include <compiler_defs.h>
#include <C8051F930_defs.h>            // SFR declarations

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

void OSCILLATOR_Init (void);
void PORT_Init (void);

//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------

void main (void)
{
   PCA0MD &= ~0x40;                    // WDTE = 0 (clear watchdog timer
                                       // enable)

   PORT_Init();                        // Initialize Port I/O
   OSCILLATOR_Init ();                 // Initialize Oscillator

   while (1);                          // Infinite Loop

}                                    

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

//-----------------------------------------------------------------------------
// OSCILLATOR_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function initializes the system clock to use the internal precision
// oscillator with spread spectrum enabled.
//
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void)
{
   
   
   OSCICN |= 0x80;                     // Enable the precision internal osc.
   OSCICL |= 0x80;                     // Enable Spread Spectrum
   
   RSTSRC = 0x06;                      // Enable missing clock detector and
                                       // leave VDD Monitor enabled.

   CLKSEL = 0x00;                      // Select precision internal osc. 
                                       // divided by 1 as the system clock
  
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the crossbar and ports pins.
//
// The oscillator pins should be configured as analog inputs when using the
// external oscillator in crystal mode.
//
// P0.0   digital    push-pull             /SYSCLK
//-----------------------------------------------------------------------------
void PORT_Init (void)
{

   // Buffered System Clock Output
   P0MDOUT |= 0x01;                    // P0.0 is push-pull

   // Crossbar Initialization
   XBR0    = 0x08;                     // Route /SYSCLK to first available pin
   XBR2    = 0x40;                     // Enable Crossbar and weak pull-ups
}

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