MSP430F149；一、基本时钟

谁借莪１个温暖的怀抱￠ 2022-04-24 15:14 172阅读 0赞

## 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 <msp430.h>
    
    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；  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70]  
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；  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70 1]

## 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.  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70 2]  
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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70 3]  
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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70 4]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70 5]  
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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzAxNzU4_size_16_color_FFFFFF_t_70 6]

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