SN8P2501D
8-Bit Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 40
Version 1.5
4.3 NOISE FILTER
The Noise Filter controlled by
“Noise_Filter” code option is a low pass filter and supports external oscillator including
RC and crystal modes. The purpose is to filter high rate noise coupling on high clock signal from external oscillator.
In high noisy environment, to enable Noise_Filter is the strongly recommendation to reduce high frequency
noise effect.
4.4 SYSTEM HIGH-SPEED CLOCK
The system high-speed clock has internal and external two-type. The external high-speed clock includes 4MHz, 12MHz,
32KHz crystal/ceramic and RC type. These high-speed oscillators are selected by
“
High_CLK
” code option. The
internal high-speed clock supports real time clock (RTC) function under
“IHRC_RTC” mode. The internal high-speed
clock and external 32KHz oscillator active under
“IHRC_RTC” mode. The internal high-speed clock is the system clock
source, and the external 32KHz oscillator is the RTC clock source to supply a accurately real time clock rate.
4.4.1 HIGH_CLK CODE OPTION
For difference clock functions, Sonix provides multi-type system high clock options controlled by
“High_CLK” code
option. The High_CLK code option defines the system oscillator types including IHRC_16M, IHRC_RTC, RC, 32K X
’tal,
12M X
’tal and 4M X’tal. These oscillator options support different bandwidth oscillator.
IHRC_16M:
The system high-speed clock source is internal high-speed 16MHz RC type oscillator. In the mode,
XIN and XOUT pins are bi-direction GPIO mode, and not to connect any external oscillator device.
IHRC_RTC:
The system high-speed clock source is internal high-speed 16MHz RC type oscillator. The RTC
clock source is external low-speed 32768Hz crystal. The XIN and XOUT pins are defined to drive external
32768Hz crystal and disables GPIO function.
RC:
The system high-speed clock source is external low cost RC type oscillator. The RC oscillator circuit only
connects to XIN pin, and the XOUT pin is bi-direction GPIO mode.
32K X
’tal:
The system high-speed clock source is external low-speed 32768Hz crystal. The option only supports
32768Hz crystal and the RTC function is workable.
12M X
’tal:
The system high-speed clock source is external high-speed crystal/ceramic. The oscillator bandwidth
is 8MHz~16MHz.
4M X
’tal:
The system high-speed clock source is external high-speed crystal/resonator. The oscillator bandwidth
is 455 KHz~8MHz.
For power consumption under
“
IHRC_RTC
” mode, internal low–speed oscillator stops, but external 32KHz crystal and
internal high-speed oscillator active under green mode. The condition is the watchdog timer can
’t be “
Always_On
”
option, or the internal low-speed oscillator actives. Internal high-speed oscillator can be stopped in inserting green
mode from slow mode and disable internal high-speed oscillator by STPHX bit.
4.4.2 INTERNAL HIGH-SPEED OSCILLATOR RC TYPE (IHRC)
The internal high-speed oscillator is 16MHz RC type. The accuracy is
±
2% under commercial condition. When the
“High_CLK” code option is “IHRC_16M” or “IHRC_RTC”, the internal high-speed oscillator is enabled.
IHRC_16M:
The system high-speed clock is internal 16MHz oscillator RC type. XIN/XOUT pins are general
purpose I/O pins.
IHRC_RTC:
The system high-speed clock is internal 16MHz oscillator RC type, and the real time clock is external
32768Hz crystal. XIN/XOUT pins connect with external 32768Hz crystal.
Fcpu of
“IHRC_16M” and “IHRC_RTC”:
Fhosc/1~Fhosc/16.
4.4.3 EXTERNAL HIGH-SPEED OSCILLATOR
The external high-speed oscillator includes 4MHz, 12MHz, 32KHz and RC type. The 4MHz and 12MHz oscillators
support crystal and ceramic types connected to XIN/XOUT pins with 20pF capacitors to ground. The 32KHz oscillator
supports crystal and ceramic types connected to XIN/XOUT pins with 27pF (Typical) capacitors to ground. The RC
type is a low cost RC circuit only connected to XIN pin. The capacitance is not below 100pF, and use the resistance to
decide the frequency.
