What is a system clock? What is a clock system? What is the function of the clock system?

1.Q: What is the system clock. What is a clock system.

A: Usually referred to as the system clock refers to the clock system, which is the oscillator (signal source), timing wake-up, frequency divider and other components of the circuit. The commonly used signal sources are crystal oscillators and RC oscillators.

2.Q: What is the function of the clock system?

A: The clock is the pulse of the embedded system, the processor core in the clock driver to complete the instruction execution, State transformation and other actions. Peripheral components perform various tasks under the clock driver, such as serial port data transmission, A/D conversion, timer counting and so on. Therefore, the clock is very important to the computer system, usually the clock system problems are also fatal, such as the oscillator does not start vibration, oscillation instability, stop vibration and so on.

As shown in Figure 1 below, ARM's clock system consists of 4 parts, divided into crystal oscillator, wake-up timer, phase-locked loop (PLL) and VPB divider. Where the crystal oscillator provides the basic clock signal for the system (frequency is Fosc). When the reset or the processor wakes up from power-down mode, the "wake-up timer" counts the input clock signal delay, allowing the internal parts of the chip to have time to initialize. The Fosc is then increased by the PLL to a frequency that meets the user's needs FCCLK,FCCLK for the CPU core. Because the CPU core is usually faster than the peripheral components, the user can set the VPB divider to reduce the FCCLK signal to a suitable value fpclk, which is used for peripheral components. The following is an introduction to the various parts and common concepts.