A few years ago, the chip manufacturing process may not be able to make a crystal into a chip, but now it can. This problem is mainly determined by practicality and cost.

The materials of the chip and the crystal are different. The chip (integrated circuit) is made of silicon, and the crystal is made of time (silicon dioxide). They cannot be done together, but they can be packaged together. It can be achieved at present, but the cost is relatively high.

What we usually call "on-chip clock" refers to the fact that there is no crystal oscillator in the chip, but an RC oscillator circuit.

If you use the internal RC oscillator instead of the external crystal oscillator, please proceed as follows:

1) For 100-pin or 144-pin products, OSC_IN should be grounded, and OSC_OUT should be left floating.

2) For products less than 100 feet, there are two connection methods:

I) OSC_IN and OSC_OUT are grounded through 10K resistors respectively. This method can improve electromagnetic compatibility performance.

Ii) Remap OSC_IN and OSC_OUT to PD0 and PD1, respectively, and then configure PD0 and PD1 as push-pull output and output '0'. This method can reduce power consumption and save 2 external resistors (compared to I above).

STM32 clock system structure diagram

It is the clock pulse of the STM32 single-chip microcomputer and the driving source of the single-chip microcomputer. To use any peripheral, the corresponding clock must be turned on. The advantage of this is that if the peripheral is not used, turning off its clock can reduce the power consumption of the system, save energy, and achieve the effect of low power consumption.

The clock of the STM32 microcontroller can be provided by the following three clock sources:

1. HSI: High-speed internal clock signal The clock (8M frequency) in the STM32 microcontroller has poor accuracy.

2 High-precision, HSE: high-speed external clock signal.

Source: 1. Health, safety and environmental protection external crystal/ceramic resonator (crystal oscillator);

II. External clock for health, safety and environmental protection users

3. LSE: Low-speed external crystal oscillator 32.768kHz mainly provides accurate clock source, generally used as RTC clock.