如何在PIC中选择定时器

哪一张照片？他们不都是一样的，特别是在不同的家庭之间。你想要一次延误，还是每一百年发生什么事？



      以下为原文

    Which PIC?
They are not all the same, particularly between different families.
Do you want a single delay, or something to happen every 100us?
 

PIC16F1938。我希望这些100U只发生在由另一个中断触发的特殊情况下。例如，IM使用比较器模块进行中断。如果有一个比较器中断，我希望PIC计数100US，并作出一个定时器中断。大概我想做的是嵌套中断（我想是这样）。



      以下为原文

    PIC16F1938. I want these 100us to happen ONLY on a special case triggered by another interrupt. For example, Im using the comparator module to make an interrupt. If there is a comparator interrupt, I want the PIC to count 100us and make a timer interrupt.
 Probably what I'm trying to do is a nested interrupt ( I think so)

最大的区别是你有一个16位定时器（定时器1）和四个8位定时器（0, 2, 4，6）2, 4和6彼此非常相同。定时器1也是唯一的，因为它可以由Fosc或FoC/4来计时。其他的只能在FoC/4或更慢的时钟。如果你的时钟是24MHz，那么100US是2400个FoSC计数，或者600个FoC/4计数。一个8位定时器可以做一个4:1的预分频器和一个150的计数。我只使用一个TMR 2, 4或6，并将PR2寄存器设置为150—1= 149。一个中断触发，而另一个中断仍在运行。在几乎所有的情况下，您不希望停留在第一个中断服务中等待100U到期。中断服务的黄金法则是：“尽可能少地清除中断，然后返回。”“尽快”。



      以下为原文

    The big difference is you have one 16 bit timer (Timer 1) and four 8 bit timers (0, 2, 4, 6)
2, 4 and 6 are prety much identical to each other.
Timer 1 is also unique in that it can be clocked by Fosc or Fosc/4. The others can only be clocked at Fosc/4 or slower.
 
If your clock is 24MHz, then 100us is 2400 Fosc counts, or 600 Fosc/4 counts.
An 8 bit timer can do that a 4:1 prescaler and a count of 150.
I'd simply use one of TMR 2, 4, or 6, and set the PR2 register to 150-1 = 149.

No. A "nested" interrupt is when one interrupt triggers while another interrupt is still running.
In almost every situation, you would NOT want to stay inside your first interrupt service waiting for the 100us to expire.
The Golden rule for interrupt services is "do the minimum required to clear the interrupt, and get back out as soon as possible".
 
 

很好的回答！谢谢！



      以下为原文

    Excellent answer! Thanks!

你也可以使用带有4:1预分频器的定时器0，并预装106，即256—150.0。你选择使用哪一个定时器高度依赖于什么可用，这取决于你选择PIC+你的应用程序使用（E）CCP和/或PWM修改。



      以下为原文

    You could also use Timer 0 with a 4:1 prescaler, and preload it with 106, which is  256-150.
 
Which timer you choose to use is highly dependent on what's available, which is determined by your choice of PIC + your application's use of (E)CCP and/or PWM modiules.