SN8P1600
8-bit micro-controller
SONiX TECHNOLOGY CO., LTD
Page 46
Revision 1.94
INTERNAL LOW-SPEED OSCILLATOR
The internal low-speed oscillator is built in the micro-controller. The low-speed clock source is a RC type oscillator
circuit. The low-speed clock can supplies clock for system clock and timer,.
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).
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 the following figure.
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
VDD (Volts)
4.00
4.50
5.00
5.50
6.00
6.50
F
Example: Measure the internal RC frequency by instruction cycle (Fcpu). The internal RC frequency is the
Fcpu multiplied by 4. We can get the Fosc frequency of internal RC from the Fcpu frequency.
B0BSET
P1M.0
; Set P1.0 to be output mode for outputting Fcpu toggle signal.
B0BSET
FCLKMD
; Switch the system clock to internal low-speed clock mode.
@@:
B0BSET
P1.0
; Output Fcpu toggle signal in low-speed clock mode.
B0BCLR
P1.0
; Measure the Fcpu frequency by oscilloscope.
JMP
@B