CMOS single-chip clock circuit diagram

Internal MCS-51 has an inverting amplifier, XTAL1, XTAL2 respectively inverting amplifier input and output, external feedback components on the composition of the future timing oscillator generates an internal clock to the various components of the microcontroller. AT89C51 belongs CMOS8 bit microprocessor, which is different from the clock circuit NMOS-type microcontroller in the structure.

　　CMOS single-chip internal (such as AT89C51) has a controllable negative feedback inverting amplifier, an external crystal oscillator (or ceramic resonator) and a capacitor oscillator, the next picture shows CMOS single-chip clock circuit diagram. Oscillators work by / PD side control, by software "1" PD (ie special function registers PCON.1) make / PD = 0, the oscillator is stopped, the entire microcontroller will stop working in order to achieve energy-saving purposes. Cleared "0" PD, so oscillator generates a clock, the microcontroller will operate normally. SYS figure for crystal or ceramic resonator, oscillator generated clock frequency is mainly determined by the SYS parameter (marked on the crystal frequency). The role of capacitors C1 and C2 are two: one is to make the oscillator start-up, the second is to fine-tune the oscillator frequency f plays the role of (C1, C2 big, f becomes smaller), which is typically 30pF.

CMOS single-chip clock circuit diagram in Figure