说说silicon labs 的单片机

C8051F系列的，它的单片机很多，最重要的就是，它改变了经典51的速度，将经典51的系统12分频给取消了，就是1分频了。新的名字叫做CIP-51.

从它们的datasheet截图下来的，增加了XRAM，系统1分频或者2分频，还有就是它增加了一些经典51没有的外设接口，比如ADC,DAC,SMBUS(IIC),JTAG和芯片内部温度传感器，等等。

我就以C8051F021芯片为例说明一下，首先供电电压，经典51那就是5V，这个芯片不是5V，下面的表格说的很清楚了，我们就选择3.3V，不过它IO都是可以耐压5V，但是有些IO不可以的，要注意。

 

 

第二，说一下它的时钟配置，学习一个新的芯片，写代码之前要搞定它的时钟。如果没有，你还是别去写代码，先搞懂时钟。我只说配置为外部CMOS时钟输入的情况，晶振，RC，C，或者自己内部时钟，请读者自己看说明书吧。

这个图足以说明一切，但是我还是要说，就是上面的那段英文，如果配置CMOS外部时钟为时钟源，XTAL1要接时钟输入脚，XTAL2可以悬空，还要注意这个时候XTAL1和XTAL2都不可以接5V，也就是说输入电压在3.3以下，你可以接5V，反正是你设计电路，烧芯片也是你负责呀。呵呵。

有2个寄存器比较重要OSCXCN和OSCICN.

只有bit6-bit4有用，其他的对该配置无用。啥意思，自己看。

各项的意思，我不翻译英文，自己看。

接下来，我们具体看看C语言如何配置

//-----------------------------------------------------------------------------

// F02x_Osc_Init.c

//-----------------------------------------------------------------------------

// Copyright 2003 Cygnal Integrated Products, Inc.

//

// AUTH: FB

// DATE: 27 DEC 02

//

// This program shows an example of configuring the internal

// and external oscillators.

//

// Target: C8051F02x

// Tool chain: KEIL C51 6.03 / KEIL EVAL C51

//

//-----------------------------------------------------------------------------

// Includes

//-----------------------------------------------------------------------------

#include // SFR declarations

//-----------------------------------------------------------------------------

// 16-bit SFR Definitions for ‘F02x

//-----------------------------------------------------------------------------

sfr16 DP = 0x82; // data pointer

sfr16 TMR3RL = 0x92; // Timer3 reload value

sfr16 TMR3 = 0x94; // Timer3 counter

sfr16 ADC0 = 0xbe; // ADC0 data

sfr16 ADC0GT = 0xc4; // ADC0 greater than window

sfr16 ADC0LT = 0xc6; // ADC0 less than window

sfr16 RCAP2 = 0xca; // Timer2 capture/reload

sfr16 T2 = 0xcc; // Timer2

sfr16 RCAP4 = 0xe4; // Timer4 capture/reload

sfr16 T4 = 0xf4; // Timer4

sfr16 DAC0 = 0xd2; // DAC0 data

sfr16 DAC1 = 0xd5; // DAC1 data

//-----------------------------------------------------------------------------

// Global CONSTANTS

//-----------------------------------------------------------------------------

sbit LED = P1^6; // LED=’1’ means ON

sbit SW1 = P3^7; // SW1=’0’ means switch pressed

//-----------------------------------------------------------------------------

// Function PROTOTYPES

//-----------------------------------------------------------------------------

void SYSCLK_IntOsc_Init (void);

void SYSCLK_Crystal_Init (void);

void SYSCLK_C_RC_Init (void);

void SYSCLK_CMOS_Init (void);

//-----------------------------------------------------------------------------

// MAIN Routine

//-----------------------------------------------------------------------------

void main (void) {

WDTCN = 0xde; // disable watchdog timer

WDTCN = 0xad;

// select one of the following functions to initialze the system clock

SYSCLK_IntOsc_Init ();

// SYSCLK_Crystal_Init ();

// SYSCLK_C_RC_Init ();

// SYSCLK_CMOS_Init ();

while (1);

}

//-----------------------------------------------------------------------------

// Initialization Subroutines

//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------

// SYSCLK_IntOsc_Init

//-----------------------------------------------------------------------------

//

// This routine initializes the system clock to use the internal oscillator

// at its maximum frequency.

//

void SYSCLK_IntOsc_Init (void)

{

OSCICN = 0x87; // Set internal oscillator to

// maximum frequency and enable missing

// clock detector

}

//-----------------------------------------------------------------------------

// SYSCLK_Crystal_Init

//-----------------------------------------------------------------------------

//

// This routine initializes the system clock to use a 22.1184MHz crystal

// as its clock source. Assumes a 22.1184 MHz crystal and associated loading

// capacitors are connected at XTAL1 and XTAL2.

//

void SYSCLK_Crystal_Init (void)

{

int i; // delay counter

OSCXCN = 0x67; // start external oscillator with

// 22.1184MHz crystal

for (i=0; i < 256; i++) ; // XTLVLD blanking interval (>1ms)

while (!(OSCXCN & 0x80)) ; // Wait for crystal osc. to settle

OSCICN = 0x88; // select external oscillator as SYSCLK

// source and enable missing clock

// detector

}

//-----------------------------------------------------------------------------

// SYSCLK_C_RC_Init

//-----------------------------------------------------------------------------

//

// This routine initializes the system clock to use an external RC network

// or a single capacitor as its clock source. Assumes an RC network is

// connected to XTAL1 or a single capacitor is connected to XTAL1 and

// XTAL2.

//

void SYSCLK_C_RC_Init (void)

{

OSCXCN = 0x47; // start external oscillator in

// C/RC mode with XFCN = 7

OSCICN = 0x88; // select external oscillator as SYSCLK

// source and enable missing clock

// detector

}

//-----------------------------------------------------------------------------

// SYSCLK_CMOS_Init

//-----------------------------------------------------------------------------

//

// This routine initializes the system clock to the external oscillator in

// CMOS clock mode. Assumes a CMOS clock generator is connected to XTAL1.

//

void SYSCLK_CMOS_Init (void)

{

OSCXCN = 0x20;                 // start external oscillator in

// CMOS clock mode.

OSCICN = 0x88;                 // select external oscillator as SYSCLK

// source and enable missing clock

// detector

}

配置为CMOS时钟源，就这两条语句就行了。