EM78P350N
8-Bit Microprocessor with OTP ROM
In the most applications, Pin OSCI and Pin OSCO can be connected with a crystal or
ceramic resonator to generate oscillation. Fig. 6-16 below depicts such a circuit. The
same applies to the HXT mode and the LXT mode.
C1
OSCI
EM78P330
XTAL
OSCO
C2
RS
Fig. 6-16 Crystal/Resonator Circuit
The following table provides the recommended values for C1 and C2. Since each
resonator has its own attribute, user should refer to the resonator specifications for
appropriate values of C1 and C2. RS, a serial resistor, may be required for AT strip cut
crystal or low frequency mode.
Capacitor selection guide for crystal oscillator or ceramic resonators:
Oscillator Type
Frequency Mode
Frequency
C1 (pF)
C2 (pF)
455 kHz
2.0 MHz
4.0 MHz
32.768 kHz
100 kHz
200 kHz
455 kHz
1.0 MHz
2.0 MHz
4.0 MHz
100~150
20~40
10~30
25
100~150
20~40
10~30
15
Ceramic Resonators
HXT
LXT
HXT
25
25
25
25
Crystal Oscillator
20~40
15~30
15
20~150
15~30
15
15
15
6.13.3 External RC Oscillator Mode
For some applications that do not require
precise timing calculation, the RC
Vcc
oscillator (Fig. 6-17 at right) offers a cost-
effective solution. Nevertheless, it should
be noted that the frequency of the RC
oscillator is influenced by the supply
voltage, the values of the resistor (Rext),
the capacitor (Cext), and even by the
operation temperature. Moreover, the
frequency also changes slightly from one
chip to another due to manufacturing
process variations.
Rext
OSCI
Cext
EM77P330
Fig. 6-17 External RC Oscillator Mode Circuit
80 •
Product Specification (V1.0) 09.14.2006
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
