pll_start.c

来自「FAT16 Filesystem on Philips LPC2000 seri」· C语言 代码 · 共 71 行

#include <stdc.h>
#include <stdio.h>
#include <types.h>
#include <LPC21xx.h>
#include <system.h>
#include <sysdefs.h>

/******************************************************************************
 *
 * Function Name: lowInit()
 *
 * Description:
 *    This function starts up the PLL then sets up the GPIO pins before
 *    waiting for the PLL to lock.  It finally engages the PLL and
 *    returns
 *
 * Calling Sequence: 
 *    void
 *
 * Returns:
 *    void
 *
 *****************************************************************************/
static void pllInit58MHz(void)
{
	// set PLL multiplier & divisor.
	// values computed from sysdefs.h
	PLLCFG = PLLCFG_MSEL | PLLCFG_PSEL;

	// enable PLL
	PLLCON = PLLCON_PLLE;
	PLLFEED = 0xAA;                       // Make it happen.  These two updates
	PLLFEED = 0x55;                       // MUST occur in sequence.

	// wait for PLL lock
	while (!(PLLSTAT & PLLSTAT_LOCK))
		continue;

	// enable & connect PLL
	PLLCON = PLLCON_PLLE | PLLCON_PLLC;
	PLLFEED = 0xAA;                       // Make it happen.  These two updates
	PLLFEED = 0x55;                       // MUST occur in sequence.
}

void lowInit(void)
{
	pllInit58MHz();
	// setup port 0 pins
	IO0CLR = P0IO_ZERO_BITS;                // clear the ZEROs output
	IO0SET = P0IO_ONE_BITS;                 // set the ONEs output
	IO0DIR = P0IO_OUTPUT_BITS;              // set the output bit direction

	// setup port 1 pins
	IO1CLR = P1IO_ZERO_BITS;                // clear the ZEROs output
	IO1SET = P1IO_ONE_BITS;                 // set the ONEs output
	IO1DIR = P1IO_OUTPUT_BITS;              // set the output bit direction

	PCONP = ((PCTIM0 | PCTIM1 | PCUART0 | PCUART1 | PCRTC |
			 PCSPI1 | PCAD0) & ~PCONP_MASK);

	// setup & enable the MAM
	MAMTIM = MAMTIM_CYCLES;
	MAMCR = MAMCR_FULL;

	// set the peripheral bus speed
	// value computed from sysdefs.h
	VPBDIV = VPBDIV_VALUE;                // set the peripheral bus clock speed
}