怎么配置时钟和计时器产生20MHz晶振

您不能通过将值写入TMR1L一次来设置速率。您需要使用Time2，它具有PR寄存器，或者您需要一个中断服务例程，它在每次翻转后重新初始化计时器值。我们需要看到您的所有代码来查看您是否做得足够。



      以下为原文

    You can't set a rate by writing a value to TMR1L once.
You either need to use TIMER2, which has a PR register, or you need an interrupt service routine which reinitialises the timer value after every rollover.
We would need to see ALL your code to see of you are doing enough.
 

谢谢兄弟。我按你的建议去做了。它工作，但没有运行其他功能的空间。整个时间控制器忙着中断。这里是代码，定义了xTalthFrime2000 000 000 It计数＝0；空隙中断ISR（空隙）{if（pRI1BIT.TMR2IF＝1）{{PIR2IF＝0；ToGGLE（））；}空主（空隙）{T2CONTITS.TMR2ON＝1；TrasabITS.RA5＝0；LababITIs.La5＝0；RCONBITS。IPEN＝1；IPR1BIT.TMR2IP＝1；＝1；int＝1；int＝1；INTCONBITE。TMR0IP＝1；Py1BIT.TMR2IE＝1；IPR1BIT.TMR2IP＝1；T2CON= 0B000 11100；PRC1L= 0B000 011110；CCP1CON＝0B00 00 1100；T2CONTITS。TMR2ON＝1；int i；而（1）{计数＝计数+1；（i＝0；I）！= 50；i++）{；} Labb.Lb0＝Labbist.Lb0；}无效切换（空隙）{LababIT.La5= ~LababITI. LA5；}。



      以下为原文

    Thanks brother. I tried as you suggested. It works but there is no room to run other functions. Whole time controller is busy with the interrupt. Here is the code,
#define _XTAL_FREQ 20000000
int count =0 ;
void toggle(void);
  void interrupt ISR(void) {
    if(PIR1bits.TMR2IF == 1) {
    PIR1bits.TMR2IF = 0;
    toggle();
  }
}
void main(void) {
  T2CONbits.TMR2ON = 1;
  TRISAbits.RA5 = 0;
  LATAbits.LA5 = 0;
  RCONbits.IPEN = 1; 
  IPR1bits.TMR2IP = 1;
  INTCONbits.GIE = 1;
  INTCONbits.PEIE = 1;
  INTCONbits.TMR0IE = 1;
  INTCON2bits.TMR0IP = 1;
  PIE1bits.TMR2IE = 1;
  IPR1bits.TMR2IP = 1;
  T2CON = 0b00000100; 
  PR2 = 0b00111011;
  CCPR1L = 0b00011110; 
  CCP1CON = 0b00001100;
  T2CONbits.TMR2ON = 1;
  int i;
  while(1) {
    count = count + 1;
    for (i=0;i!=50;i++)   {
      ;
    }
  LATBbits.LB0 = ~LATBbits.LB0 ;
  }
}
void toggle(void) {
LATAbits.LA5 = ~LATAbits.LA5;
}

可以忽略计时器0配置位。



      以下为原文

    you can ignore timer 0 config bits. 

这意味着什么？当中断服务没有处理时，为什么启用Time0中断？当只有一个中断服务时，为什么要启用中断优先级？



      以下为原文

   
What does this mean?
Why are you enabling Timer0 interrupts when your interrupt service is not handling them?
Why are you enabling interrupt priorities when you only have a single interrupt service?

在我们的应用中，我想用这个脉冲来驱动伺服电机，速度控制（脉冲频率）和旋转控制（脉冲数）。我认为这是不可能的PWM生成，所以我试图找出一个PWM和中断的组合。同时，我们的最大脉冲频率要求是200 kHz，这是不可能的定时器中断。请指正。如果你有任何解决方案，我可以请你分享吗？谢谢



      以下为原文

    In our application, I want to use this pulse to drive a servo motor, with speed control (frequency of the pulse) and rotation control (number of pulses). Which I believe not possible with PWM generation, So I was trying to figure out a combination of PWM and interrupt. At the same time, our max pulse frequency requirement is 200KHz, which is not possible with timer interrupt. Please correct me. And if you have any solution, May I request you to share ? Thanks

如果你不理睬我的问题，就没有帮助。



      以下为原文

    If you just ignore my questions there's no point trying to help.
 

我并没有忽视，我只是试图回答你的问题。我试图使用定时器0来生成脉冲，但是那些配置位在发送代码时没有注释。这就是为什么我说，忽略计时器0配置位。



      以下为原文

    I am not ignoring, I am trying to answer your question only.
I was trying to use Timer 0 to generate pulse, but those config bits were not commented while send you the code. that is why I said, ignore Timer 0 config bits. 

这是一个问题。我问了三。



      以下为原文

    That's one question. I asked three.
 

我能用20MHz的晶体PIC18F45 50产生200 kHz脉冲，并计数脉冲数吗？



      以下为原文

    Can I generate 200KHz pulse with PIC18F4550 with 20MHz crystal,  With counting the number of pulse?

我认为你是运行在32 MHz的FoSC，所以8MHz的指令周期。8M/200K＝40个指令每脉冲，因此使用计时器产生200kHz脉冲将使用几乎所有的处理器周期。也许您应该考虑使用CCP模块在PWM模式下生成脉冲而不涉及软件。



      以下为原文

    I think you are running at 32MHz Fosc, so 8MHz instruction cycle. 8M/200K = 40 instructions per pulse, so using a timer to generate 200KHz pulses is going to use pretty much all of the processor cycles.
 
Probably you should consider using a CCP module in PWM mode to generate the pulses without software involvement.
 

谢谢你的夸奖。我说服自己，200K是困难的PIC18F45 50。



      以下为原文

    Thanks mbrowning. I convince myself that 200K is difficult with PIC18F4550.