SN8P2200 Series
USB 1.1 Low-Speed 8-Bit Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 49
Version 1.7
4
SYSTEM CLOCK
4.1
OVERVIEW
The micro-controller is a dual clock system. There are high-speed clock and low-speed clock. The high-speed clock is
generated from the external oscillator circuit or on-chip 6MHz high-speed RC oscillator circuit (IHRC 6MHz). The
low-speed clock is generated from on-chip low-speed RC oscillator circuit (ILRC 16KHz @3V, 32KHz @5V).
Both the high-speed clock and the low-speed clock can be system clock (Fosc). The system clock in slow mode is
divided by 4 to be the instruction cycle (Fcpu).
)
Normal Mode (High Clock):
Fcpu = Fhosc / N
, N = 1 ~ 4, Select N by Fcpu code option.
)
Slow Mode (Low Clock):
Fcpu = Flosc/4.
4.2
CLOCK BLOCK DIAGRAM
Fhosc.
Fcpu = Fhosc/1 ~ Fhosc/4
Flosc.
Fcpu = Flosc/4
CPUM[1:0]
XIN
XOUT
STPHX
HOSC
Fcpu Code Option
Fosc
Fosc
CLKMD
Fcpu
z
HOSC: High_Clk code option.
z
Fhosc: External high-speed clock (only 6MHz) / Internal high-speed RC clock (6MHz).
z
Flosc: Internal low-speed RC clock (about 16KHz@3V, 32KHz@5V).
z
Fosc: System clock source.
z
Fcpu: Instruction cycle.