Samsung S5PC100, User Manual

Page: 173 / 1863

S5PC100 USER’S MANUAL (REV1.0) CLOCK CONTROLLER
2.3-23
8 I/O DESCRIPTION
Funtion
Signal
I/O Description Pad Type
CLKOUT Out Clock monitoring pad XCLKOUT Dedicated
XTI & XTO Input &
Output
Oscillator pads for system clock
XXTI & XXTO Dedicated
USB_XTI &
USB_XTO Input &
Output
Oscillator pads for USB clock or system clock
XusbXTI &
XusbXTO
Dedicated
27M_XTI &
27M_XTO Input &
Output
Oscillator pads for TV clock
X27mXTI &
X27mXTO
Dedicated
NOTE: Type field indicates whether pads are dedicated to the signal or pads are connected to the multiplexed signals.
When a clock pad is not used, the input clock pad should be connected to GND.
8.1 DRIVER STRENGTH OF OSCILLATOR PAD
Driver strength of oscillation pads (XT, XT_USB, and XT_27M) must be set rightly, according to input frequency.
DRV value Output Freq
2’b00 Driver X1 32kHz ~ 1MHz
2’b01 Driver X2 1MHz ~ 15MHz
2’b10 Driver X3 15MHz ~ 30MHz
2’b11 Driver X4 30MHz ~ 50MHz
To get more information, refer to “ETC4DRV SFR in 02.02 S5PC100_GPIO”.
8.2 CRYSTAL OSCILLATOR DESIGN CONSIDERATION
The external components commonly used for the oscillator circuit are a resonator (quarts crystal), two capacitors
CL and two resistors Rf and Rs, as shown in the below figure.
XXTI needs 12MHz crystal oscillator. XusbXTI also needs 12MHz crystal oscillator to be used as main system
clock by the setting of OM[0]=1. XXTI27 needs 27MHz crystal oscillator.
For 12MHz or 27MHz crystal oscillator, the following values of external components are recommended;