SN8P2318 Series
C-type LCD, RFC 8-Bit Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 46
Version 1.5
4
4
4
SYSTEM CLOCK
4.1 OVERVIEW
The micro-controller is a dual clock system including high-speed and low-speed clocks. The high-speed clock includes
internal high-speed oscillator and external oscillators selected by
“High_Clk” code option. The low-speed clock is
external low-speed oscillator. Both high-speed clock and external low-speed clock can be system clock source through
a divider to decide the system clock rate.
High-speed oscillator
Internal high-speed oscillator is 16MHz PLL type called
“
PLL_16M
”.
External high-speed oscillator includes crystal/ceramic (4MHz, 12MHz) and RC type.
Low-speed oscillator
External low-speed oscillator includes crystal/ceramic (32KHz) and RC type.
System clock block diagram
Fhosc.
Fcpu = Fhosc/1 ~ Fhosc/16, Noise_Filter Disable
Fcpu = Fhosc/4 ~ Fhosc/16, Noise_Filter Enable
Flosc.
Fcpu = Flosc/4
CPUM[1:0]
XIN
XOUT
STPHX
HOSC
Fcpu Code Option
Fosc
Fosc
CLKMD
Fcpu
PLL
LXIN
LXOUT
LOSC
HOSC: High_Clk code option.
LOSC: Low_Clk code option.
Fhosc: External high-speed clock / Internal PLL clock.
Flosc: External low-speed clock.
Fosc: System clock source.
Fcpu: Instruction cycle.
4.2 FCPU (INSTRUCTION CYCLE)
The system clock rate is instruction cycle called
“
Fcpu
” which is divided from the system clock source and decides the
system operating rate. Fcpu rate is selected by Fcpu code option and the range is
Fhosc/1~Fhosc/16
under system
normal mode. If the system high clock source is external 4MHz crystal, and the Fcpu code option is Fhosc/4, the Fcpu
frequency is 4MHz/4 = 1MHz. Under system slow mode, the Fcpu is fixed Flosc/4, 32KHz/4=8KHz.
4.3
SYSTEM HIGH-SPEED CLOCK
The system high-speed clock has internal and external two-type. The external high-speed clock includes 4MHz, 12MHz,
crystal/ceramic and RC type. The internal high-speed clock is internal PLL 16MHz oscillator. These high-speed
oscillators are selected by
“
High_Clk
” code option.