How do Multiply Frequence by CPU?

Question

Hi can anyone description ,about mul frequence in CPU?for example how a 200k frequnce convert to up 500k frequence by CPU.

Answer 1

Your question is not specific enough to answer directly so I will attempt to answer the interpretations I have of it. There are two things you could be referring to. First, many CPUs have clock circuits built in in which you give them a clock frequency and they will multiply it up so that internally they operate at some integer multiple of it. Second, you can use a CPU running at some higher clock speed to generate a sequence of pulses at a higher frequency when a slower pulse train is received by it.

In the first case, the CPU has a phase lock loop circuit within it to multiply the incoming clock frequency up by an integer amount to operate the CPU internally at a much faster clock frequency. The phase locked loop (PLL) is described in the link below.
Note that this case is for use by the CPU itself and has nothing to do with a program running on it.

In the second case, some external signal drives an I/O pin of the CPU and is used to trigger the generation of a series of pulses at a faster rate by the CPU firmware. A program can be written to operate on the CPU which monitors the I/O pin and when an edge is detected, it will cause a series of pulses to be emitted from another I/O pin. A digital phase locked loop can be implemented that will generate a faster series of pulses on an output pin in response to a pulse on the input pin. This will effectively multiply the incoming frequency, but is relying on the processor being clocked by a much higher frequency clock anyway.