EM78P468NBQ EMC [ELAN Microelectronics Corp], EM78P468NBQ Datasheet - Page 40

• Manufacturer Part Number: EM78P468NBQ
• Description: 8-BIT Microcontroller
• Manufacturer: EMC [ELAN Microelectronics Corp]

EM78P468N
8-BIT Microcontroller
36 •
4.6.3
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 a
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
EM78P468N
Crystal Oscillator
R-OSCI
OSCO
CLK1
X
0
0
1
1
XTAL
Ceramic
Resonators
Crystal Oscillator
Crystal Oscillator
Rs
Oscillator Type
CLK0
X
0
1
0
1
Fig.9 Circuit for External Clock Input
Fig. 10 Circuit for Crystal/Resonator
/Ceramic Resonators (XTAL)
EM78P468N
C1
C2
R-OSCI
OSCO
Fs*130
Fs*65
Fs*65/2
Fs*65/4
Fs*244
Main clock
(This specification is subject to change without further notice)
Frequency
32.768kHz
455 kHz
2.0 MHz
455KHz
4.0MHz
1.0MHz
2.0MHz
4.0MHz
EM78P468N
Product Specification (V1.2) 03.15.2005
Xout
Xin
Example Fs=32.768K
4.26 MHz
2.13 MHz
1.065 MHz
5
8
32 KHz
MHz
100~150
XTAL
C1 (pF)
20~40
10~30
20~40
15~30
Rs
15
15
25
C1
C2
100~150
C2 (pF)
20~150
20~40
10~30
15~30
s shown in
15
15
25