Clock cycle

Clock cycle ： The clock period is also called oscillation period , Defined as the reciprocal of the clock frequency . The clock cycle is the most basic in a computer 、 The smallest unit of time . In a clock cycle ,CPU Complete a basic action .

  A clock cycle is an amount of time , People stipulate that 10 nanosecond （ns） For one clock cycle . The clock cycle represents SDRAM Maximum frequency of operation . Smaller clock cycles mean higher operating frequencies . about PC100 Specifications of memory , Its operating clock cycle should not be higher than 10 nanosecond . The conversion relationship between nanosecond and operating frequency is :1000/ Clock cycle = Working frequency , for example , Nominal 10 Nanosecond PC100 Memory chip , The expression of its working frequency should be 1000/10=100MHE, This indicates that the rated working frequency of this memory chip is 100MHE. At present, some memory with excellent quality on the market can usually work at a higher frequency than the rated frequency , This brings great convenience to some friends who like overclocking . for example KingMAX Of PC100 Memory , This kind of memory mostly adopts 8 Nanosecond chip , be relative to 100MHZ In terms of frequency , There is still much room for frequency improvement , Many users can let them work in 133MHZ Even higher frequencies . Whether overclocking can be used largely reflects the memory chip and PCB Quality of plate . however , It is not enough to judge the speed of memory only by the clock cycle , Memory CAS The access time and delay time also determine the performance of memory to a certain extent .

The clock cycle is determined by CPU A fixed time interval defined by a clock , yes CPU The smallest unit of time for work , Also called beat pulse or T cycle .

Simple understanding

The input and output interface controls the data block transmission between the main memory and peripheral devices , Without the need for CPU To control the transmission of each byte . This transmission mode is called direct memory access mode .

SCM clock cycle

Clock cycle is the basic time unit of MCU .

Two oscillation periods （ Clock cycle ） Form a state cycle .

If the oscillation frequency of the clock crystal oscillator is fosc, Then the clock cycle tosc=1/fosc.（ It is the reciprocal of the oscillation period ） Such as ： The crystal oscillator frequency is 12MHZ, Then the clock cycle tosc=1/12us