ST7FOXK2 datasheet(39/226 Pages) STMICROELECTRONICS

39 / 226 page

ST7FOXF1, ST7FOXK1, ST7FOXK2

Supply, reset and clock management

39/226

6.2.1

External clock source

In this external clock mode, a clock signal (square, sinus or triangle) with ~50% duty cycle

has to drive the OSC1 pin while the OSC2 pin is tied to ground.

Note:

When the Multi-Oscillator is not used OSCI1 and OSCI2 must be tied to ground, and PB1 is

selected by default as the external clock.

6.2.2

Crystal/ceramic oscillators

In this mode, with a self-controlled gain feature, oscillator of any frequency from 1 to 16 MHz

can be placed on OSC1 and OSC2 pins. This family of oscillators has the advantage of

producing a very accurate rate on the main clock of the ST7. In this mode of the multi-

oscillator, the resonator and the load capacitors have to be placed as close as possible to

the oscillator pins in order to minimize output distortion and start-up stabilization time. The

loading capacitance values must be adjusted according to the selected oscillator.

These oscillators are not stopped during the RESET phase to avoid losing time in the

oscillator start-up phase.

6.2.3

Internal RC oscillator

In this mode, the tunable RC oscillator is used as main clock source. The two oscillator pins

have to be tied to ground.

The calibration is done through the RCCRH[7:0] and RCCRL[6:5] registers.

Table 8.

ST7 clock sources

Hardware configuration

OSC1

OSC2

EXTERNAL

ST7

SOURCE

ST7FOXK2 数据表(PDF) 39 Page - STMicroelectronics