PFS172 datasheet(31/92 Pages) PADAUK

31 / 92 page

PFS172

8bit MTP MCU with 8-bit ADC

Page 31 of 92

PDK-DS-PFS172-EN_V000-May 8, 2020

(6) .ADJUST_IC

SYSCLK=ILRC, IHRC=16MHz, VDD=5V

After boot up, CLKMD = 0XE4：



IHRC frequency is calibrated to 16MHz@VDD=5V and IHRC module is disabled



System CLK = ILRC



Watchdog timer is disabled, ILRC is enabled, PA5 is input mode

(7) .ADJUST_IC

DISABLE

After boot up, CLKMD is not changed (Do nothing)：



IHRC is not calibrated and IHRC module is disabled by Boot-up Time



System CLK = ILRC or IHRC/64 (by Boot-upTime)



Watchdog timer is enabled, ILRC is enabled, PA5 is in input mode

5.4.4. External Crystal Oscillator

If crystal oscillator is used, a crystal or resonator is required between X1 and X2. Fig.2 shows the hardware

connection under this application; the range of operating frequency of crystal oscillator can be from 32 KHz to

4MHz, depending on the crystal placed on; higher frequency oscillator than 4MHz is NOT supported.

Fig.2: Connection of crystal oscillator

Besides crystal, external capacitor and options of PFS172 should be fine tuned in eoscr (0x0a) register to

have good sinusoidal waveform. The eoscr.7 is used to enable crystal oscillator module, eoscr.6 and eoscr.5

are used to set the different driving current to meet the requirement of different frequency of crystal oscillator:



eoscr.[6:5]=01 : Low driving capability, for lower frequency, ex: 32KHz crystal oscillator



eoscr.[6:5]=10 : Middle driving capability, for middle frequency, ex: 1MHz crystal oscillator



eoscr.[6:5]=11 : High driving capability, for higher frequency, ex: 4MHz crystal oscillator

Table 4 shows the recommended values of C1 and C2 for different crystal oscillator; the measured start-up

time under its corresponding conditions is also shown. Since the crystal or resonator had its own

characteristic, the capacitors and start-up time may be slightly different for different type of crystal or

PA7/X1

PA6/X2

The values of C1 and C2 should depend on

the specification of crystal.

eoscr.7

(Enable crystal oscillator)

eoscr[6:5]

(Select driving current for oscillator)

System clock = EOSC

PA7/X1

PA6/X2

System clock = EOSC

PA7/X1

PA6/X2

The values of C1 and C2 should depend on

the specification of crystal.

eoscr.7

(Enable crystal oscillator)

eoscr[6:5]

(Select driving current for oscillator)

System clock = EOSC

PA7/X1

PA6/X2

System clock = EOSC

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