em78p468l ELAN Microelectronics Corp, em78p468l Datasheet - Page 37

• Manufacturer Part Number: em78p468l
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.5) 02.15.2007
(This specification is subject to change without further notice)
6.6.3
EM78P468N
Bits 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.6-7 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. 6-8 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
R-OSCI
0
0
0
0
1
OSCO
Crystal Oscillator/Ceramic Resonators (Crystal)
CLK1
XTAL
Rs
0
0
1
1
×
Ceramic Resonators
Crystal Oscillator
Crystal Oscillator
Oscillator Type
CLK0
C1
C2
0
1
0
1
×
Fig. 6-8 Circuit for Crystal/Resonator
Fig. 6-7 External Clock Input Circuit
EM78P468N
R-OSCI
OSCO
Fs×130
Fs×65
Fs×65/2
Fs×65/4
Fs×244
Main clock
EM78P468N
Frequency
32.768kHz
2.0 MHz
455 kHz
4.0MHz
1.0MHz
2.0MHz
4.0MHz
455kHz
Xout
Xin
XTAL
Rs
EM78P468N/EM78P468L
Example Fs=32.768KHz
4.26 MHz
2.13 MHz
1.065 MHz
532 kHz
8 MHz
100~150
C1 (pF)
20~40
10~30
20~40
15~30
15
15
25
C1
C2
8-Bit Microcontroller
100~150
C2 (pF)
20~150
20~40
10~30
15~30
15
15
25
• 31