2019年10月25日 | MSP430F149；一、基本时钟

TI官方的提供的代码

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

//  MSP-FET430P140 Demo - Basic Clock, Output Buffered SMCLK, ACLK and MCLK

//

//  Description: Output buffered MCLK, SMCLK and ACLK.

//  ACLK = LFXT1 = 32768, MCLK = DCO Max, SMCLK = XT2

//  //* XTAL's REQUIRED - NOT INSTALLED ON FET *//

//  //* Min Vcc required varies with MCLK frequency - refer to datasheet *//

//

//                MSP430F149

//            -----------------

//        /||              XIN|-

//         | |                 | 32k

//         --|RST          XOUT|-

//           |                 |

//           |            XT2IN|-

//           |                 | XTAL (455k - 8Mhz)

//           |RST        XT2OUT|-

//           |                 |

//           |             P5.4|-->MCLK = DCO Max

//           |             P5.5|-->SMCLK = XT2

//           |             P5.6|-->ACLK = 32kHz

//

//  M. Buccini

//  Texas Instruments Inc.

//  Feb 2005

//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.21A

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

#include

int main(void)

{

  WDTCTL = WDTPW +WDTHOLD;                  // Stop Watchdog Timer

  DCOCTL = DCO0 + DCO1 + DCO2;              // Max DCO

  BCSCTL1 = RSEL0 + RSEL1 + RSEL2;          // XT2on, max RSEL

  BCSCTL2 |= SELS;                          // SMCLK = XT2

  P5DIR |= 0x70;                            // P5.6,5,4 outputs

  P5SEL |= 0x70;                            // P5.6,5,5 options

  while(1)

  {

  }

}

简单说明

这里用到了

DCOCTL ；BCSCTL1；BCSCTL2 ；//寄存器

并通过P5.6,5,4 引脚的第二功能输出对应时钟频率。

有兴趣的可以直接拷入代码试试，用示波器来看对应的时钟频率；

时钟说明

由下图可以知道，ACLK的时钟只能是有LFXT1CLK提供；

MCLK由XT2CLK或者DCOCLK或者LFXT1CLK提供；主要设置SELMx；

SMCLK由XT2CLK或者DCOCLK提供；主要设置SELS；

寄存器说明

配置好时钟主要看懂以下5个寄存器就好，算是比较容易了，刚开始比较麻烦，后来看了带锁频器的F5438A有9个寄存器来控制时钟系统，突然觉得这个还是可以接受的，哭脸一个.

上面的注意有一个复位是用POR不是PUC；

DCOCTL是调制DCOCLK时钟源的频率的（所以说，这个是个可调频率的振荡器，不是市面上卖的那种，是多少就是多少那种）；对定时要求不是特别严格的，可以直接用默认的就好；

DCOx主调

MODx微调

1&2就是开始做选择了，时钟的分频呀啥啥啥的，哎，其实还好，比5.1稍稍麻烦一点点而已

两个中断相关寄存器。中断使能位和中断标志位。

两个寄存器目前用到了这两位，就先写出这两位，其他位其实是有东西的