Samsung S5PC100 User Manual page 173

S5PC100 USER'S MANUAL (REV1.0)
8 I/O DESCRIPTION
Funtion I/O
Signal
CLKOUT Out
XTI & XTO Input &
Output
USB_XTI & Input &
USB_XTO Output
27M_XTI & Input &
27M_XTO Output
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
2'b00
2'b01
2'b10
2'b11
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;
Description
Clock monitoring pad
Oscillator pads for system clock
Oscillator pads for USB clock or system clock
Oscillator pads for TV clock
Output
Driver X1
Driver X2
Driver X3
Driver X4
CLOCK CONTROLLER
Pad
XCLKOUT Dedicated
XXTI & XXTO Dedicated
XusbXTI & Dedicated
XusbXTO
X27mXTI & Dedicated
X27mXTO
Freq
32kHz ~ 1MHz
1MHz ~ 15MHz
15MHz ~ 30MHz
30MHz ~ 50MHz
Type
2.3-23