pll.c

基于51的单片机的PPP协议实现

/*/////////////////////////////////////////////////////////////////////////////

File Name : Pll.c

Author : Rene Trenado

Location : Motorola Applications Lab, Baja California

Date Created : September 2000

Current Revision : 0.0

Notes : This file contains the code of the InitPll function

//////////////////////////////////////////////////////////////////////////////*/

#include "pll.h"



/***********************************************************************
Function : 	InitPll

Parameters : 	None

Date : 		September 2000

Desc : 		Initializes the PLL to operate at 4.91520 MHz

***********************************************************************/
#asm
	xdef	_InitPLL

_InitPLL:
	BCLR    5,0x36              	;turn off PLL so it can be initialized
	MOV		  #0x00,0x38	;Set multiplier for 4.9152MHz
  	MOV		  #0x96,0x39	;see manual for calculations
	MOV		  #0x80,0x3A	;Set range select
  	BSET    7,0x37			;Allow automatic acquisition & tracking
	BSET    5,0x36			;turn PLL back on
HERE:
  	BRCLR	  6,0x37,HERE		;Wait for PLL to lock
	BSET	  4,0x36		;Select PLL as Source

#endasm