EM78468
8-BIT Microcontroller
Bit 6~4 (CLK2~0) of RD: main clock selection bits for PLL mode (code option select)
CLK2
CLK1
CLK0
Main clock
Example Fs=32.768K
0
0
0
0
1
0
0
1
1
X
0
1
0
1
X
Fs*130
Fs*65
Fs*65/2
Fs*65/4
Fs*244
4.26 MHz
2.13 MHz
1.065 MHz
532 KHz
8 MHz
4.6.3 Crystal Oscillator/Ceramic Resonators (XTAL)
This LSI can be driven by an external clock signal through the R-OSCI pin as shown in
Fig.9 below.
In most applications, the R-OSCI pin and the OSCO pin can be connected with a crystal
or ceramic resonator to generate oscillation. Fig. 10 depicts such circuit. Table 5
provides the recommended values of C1 and C2. Since each resonator has its own
attribute, user should refer to its specification for appropriate values of C1 and C2. RS, a
serial resistor, may be necessary for AT strip cut crystal or low frequency mode.
R-OSCI
OSCO
Fig.9 Circuit for External Clock Input
C1
C1
C2
R-OSCI
OSCO
Xin
XTAL
Rs
XTAL
Rs
Xout
C2
Fig. 10 Circuit for Crystal/Resonator
Table 5 Capacitor Selection Guide for Crystal Oscillator or Ceramic Resonators
Oscillator source Oscillator Type
Frequency
455 kHz
2.0 MHz
4.0MHz
455KHz
1.0MHz
C1 (pF)
100~150
20~40
10~30
20~40
15~30
15
C2 (pF)
100~150
20~40
10~30
20~150
15~30
15
Ceramic
Resonators
Main oscillator
Crystal Oscillator
2.0MHz
4.0MHz
15
15
Sub-oscillator
Crystal Oscillator
32.768kHz
25
25
Product Specification (V1.1) 04.11.2005
• 37
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
