EM78468AQ EMC [ELAN Microelectronics Corp], EM78468AQ Datasheet - Page 41

• Manufacturer Part Number: EM78468AQ
• Description: 8-BIT Microcontroller
• Manufacturer: EMC [ELAN Microelectronics Corp]

Product Specification (V1.1) 04.11.2005
(This specification is subject to change without further notice)
4.6.3 Crystal Oscillator/Ceramic Resonators (XTAL)
Bit 6~4 (CLK2~0) of RD: main clock selection bits for PLL mode (code option select)
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.
Table 5 Capacitor Selection Guide for Crystal Oscillator or Ceramic Resonators
Main oscillator
Sub-oscillator
Oscillator source
CLK2
0
0
0
0
1
CLK1
X
0
0
1
1
R-OSCI
OSCO
Ceramic
Resonators
Crystal Oscillator
Crystal Oscillator
Oscillator Type
CLK0
XTAL
X
0
1
0
1
Rs
Fig.9 Circuit for External Clock Input
Fig. 10 Circuit for Crystal/Resonator
C1
C2
Fs*130
Fs*65
Fs*65/2
Fs*65/4
Fs*244
R-OSCI
Main clock
OSCO
Frequency
32.768kHz
2.0 MHz
455 kHz
455KHz
4.0MHz
1.0MHz
2.0MHz
4.0MHz
Xout
Xin
Example Fs=32.768K
XTAL
Rs
100~150
C1 (pF)
20~40
10~30
20~40
15~30
15
15
25
4.26 MHz
2.13 MHz
1.065 MHz
532 KHz
8 MHz
8-BIT Microcontroller
C1
C2
100~150
EM78468
C2 (pF)
20~150
20~40
10~30
15~30
15
15
25
• 37