请问电源和晶体值之间有什么关系吗？PIC在正常条件下运行4MHz需要多少电压？

您好，您将需要微控制器的数据表：HTTP://www. MigCHIP.COM/WWWORDSTMS/En/PIC18F420查找：&文档：在网页的某个地方。您确定您是否有PIC18F420或PIC18LF420设备？是的，所需振荡器频率与非必需电源电压之间有关系。请参阅数据表第26章。电气特性：见第323页：LFand第322页：弗雷加德，Mysil



      以下为原文

    Hi,
You will need Datasheet for the microcontroller:
http://www.microchip.com/wwwproducts/en/PIC18F4520
Look for: > Documentation: somewhere down in the webpage.
Are you Sure whether you have a PIC18F4520 or a PIC18LF4520 device?
 
Yes, there is a relationship between wanted oscillator frequency and nessesary power supply voltage.
Look in datasheet Chapter 26.   Electrical Characteristics:
See page 323:  LFand page 322:  F
 
Regards,
   Mysil

谢谢Mysil…在复位引脚输入电压应该等于输入电压到控制器…？电源电压和复位引脚电压应相同…



      以下为原文

    Thank you Mysil...
 
At reset pin the input voltage should equal to input voltage to the controller..?
 
Power supply voltage and reset pin voltage should be same..?

嗨，是的，电源电压和复位引脚电压应该是一样的，当单片机想要自己正常运行时。但是，当你希望PIC复位时，MCLR信号必须达到0，又名0。VSS-AKAGND当编程闪存程序存储器时，M/CLR管脚上的电压可能比电源电压高。当微控制器连接到一个编程/调试工具，如PICkit，工具必须能够控制复位引脚上的电压。最常见的解决方案是在电源引脚和复位引脚之间连接一个10kOhm的电阻。在数据表中的某个地方，有一个更复杂的问题D图，有一个大胆的解释。在任何情况下，程序员连接必须直接到/MCLR引脚。也有可能对没有高于电源Vdd的电压的微控制器进行编程。为了实现这一点，还有一个引脚：PGM，它也必须连接到编程工具。



      以下为原文

    Hi,
Yes,
Power supply voltage and reset pin voltage should be same, when microcontroller is wanted to run normally on it's own.
But when you want the PIC to Reset, the MCLR signal must be brought to 0, aka. Vss aka. GND
When Programming the Flash program memory, voltage on the /MCLR pin may be brought Higher than Power supply voltage. When the microcontroller is connected to a Programming / Debugging tool, like PICkit, the tool Must be able to control the voltage on the reset pin.
 
The most common solution is to connect a 10 kOhm resistor between power supply pin and reset pin.
Somewhere in the Datasheet, there is a more complicated diagram, with a bougous explaination. 
In any case, the Programmer connection must be directly to the /MCLR pin.
 
There is also a possibility to program the microcontroller with no voltage higher than power supply Vdd.
For this to work, there is another pin: PGM that also must be connected to the Programmer tool.
 
Regards,
   Mysil
 
 

虽然它只需要像PIC18F420这样的老处理器。较新的部件在没有额外的销钉的情况下也一样。



      以下为原文

   
Although it's only a requirement with old processors like the PIC18F4520.
Newer parts do the same without an extra pin.

同意，但是这个线程从一开始就是关于PIC18F4520的。PIC32设备一直只使用内部编程电压进行编程，MCLR管脚上不允许有高电压。随着PIC16设备开发板的深入，微芯片似乎越来越促进LVP编程。浅谈LVP程序设计。迈西尔



      以下为原文

    Agree,
but this thread have been about PIC18F4520 from the beginning.
 
PIC32 devices have always been programmed using internal programming voltage only, with no high voltage allowed on MCLR pin.
 
Microchip seem to increasingly promote LVP programming, with new development boards for PIC16 devices depending on LVP programming.
 
   Mysil