system.c

用Freescale的8位单片机做的RS232-CAN的通讯转换板.包含固件程序,原理图,PCB图和一个说明文件.

#include "system.h"
#include "mc68hc908gz32.h"

void InitSystem(void)
{
	Setfbus();
	SetPort();
	return;
}

void Setfbus(void)
{

//  fBUSDES = 8MHz
//  fVCLKDES = 4 * 8 = 32MHz
//	fRCLK = 8MHz
//	fVCLK = (N) * fRCLK = 8MHz
//  N = 32 / 8 = 4
//	E = 2
//	L = Round(fVCLK / (2^E * fNOM)) :fNOM = 71.4kHz
//    = Round(32000 / 71.4) = 112 = $70

 

	PCTL = 0x00;
	PBWC = 0x080;		//
	
	
	PCTL = 0x002;		//E
		 
	PMSL = 0x004;		//N
	PMSH = 0x000;
	
	PMRS = 0x070;		//L

	PCTL = 0x22;		//打开PLL 
	PBWC_AUTO = 1;		//自动方式
	while(!PBWC_LOCK);	//等待锁定
	PCTL_BCS = 1;		//开始使用                          
	
	return;
}

void SetPort(void)
{
	DDRA = 0x0F0;
	PTA = 0x000;
}