Is twelve clock cycles is a machine cycle
The microcontroller 12 is a standard frequency dividing operation speed is 1/12 microcontroller crystal, referring to 12 cycles counted as one cycle, i.e., corresponding to the frequency by a factor of 12 points.
Parts are in the microcontroller runs with a machine cycle in the frequency oscillator 12. In layman's microcontroller register add operation is completed, exactly one machine cycle. And the clock period of 1 / 12mhz = 1 / 12us; machine cycle clock cycles = 12 = 12 * 1 / 12us = 1us ; time of the timer is a need to add each of 1us.
Crystal: refers to a crystal oscillator from a quartz body according to the cut sheet at a certain azimuth (referred to as a wafer), quartz crystal resonators, simply referred to as crystals or crystal oscillator.
Division is to reduce the relatively high frequency clock signal, the clock signal frequency is reduced to a fraction of the original frequency. For example, the microcontroller crystal frequency is 12MHz, the clock signal is 12M, was divided by 12, is the original frequency in addition to 12 to obtain a clock signal of 1MHz, this periodic signal is the machine cycle can be seen, the machine cycle becomes long, and the original 12 times the clock period. The lower the frequency, the longer the period.
