SONIX SN8P27142_2715, User Manual

Page: 52 / 130

SN8P2714X_2715
8-bit micro-controller build-in 12-bit ADC
SONiX TECHNOLOGY CO., LTD
Page 52
V1.4
7.2 INTERNAL LOW-SPEED OSCILLATOR
The internal low-speed oscillator is built in the micro-controller. The low-speed clock’s source is a RC type oscillator
circuit. The low-speed clock can supplies clock for system clock, timer counter, watchdog timer, and so on.
 Example: Stop internal low-speed oscillator.
B0BSET FCPUM0 ; To stop external high-speed oscillator and internal low-speed
; oscillator called power down mode (sleep mode).
¾ Note: The internal low-speed clock can’t be turned off individually. It is controlled by CPUM0 bit of OSCM
register.
The low-speed oscillator uses RC type oscillator circuit. The frequency is affected by the voltage and temperature of
the system. In common condition, the frequency of the RC oscillator is about 16KHz at 3V and 32KHz at 5V. The
relative between the RC frequency and voltage is as following.
Internal RC vs. VDD
7.329
8.663
11.998
15.333
18.668
22.003
25.338
28.673
32.008
35.343
38.678
0
5
10
15
20
25
30
35
40
1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50
VDD (Volts)
Fintrc (KHz)
Figure 7-5. Internal RC vs. VDD Diagram
 Example: To measure the internal RC frequency is by instruction cycle (Fcpu). The internal RC frequency is
the Fcpu multiplied by 4. So we can get the Fosc frequency of internal RC from the Fcpu
frequency.
B0BSET P2M.0 ; Set P2.0 to be output mode for outputting Fcpu toggle signal.
B0BSET FCLKMD ; Switch the system clock to internal low-speed clock mode.
@@:
B0BSET P2.0 ; Output Fcpu toggle signal in low-speed clock mode.
B0BCLR P2.0 ; Measure the Fcpu frequency by oscilloscope.
JMP @B