Crystal Oscillator/Ceramic Resonators (Crystal) - IBM MiEM78P468L Product Specification

Bits 6~4 (CLK2~0) of RD: main clock selection bits for PLL mode (code option select)
CLK2
0
0
0
0
1
6.6.3

Crystal Oscillator/Ceramic Resonators (Crystal)

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