IBM EM78P259N/260N User Manual
EM78P259N/260N
8-Bit Microprocessor with OTP ROM
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Product Specification (V1.2) 05.18.2007
(This specification is subject to change without further notice)
6.11.2 Crystal Oscillator/Ceramic Resonators (Crystal)
The EM78P259N/260N can be driven by an external clock signal through the OSCI pin
as illustrated below.
as illustrated below.
OSCI
OSCO
EM78P259N
EM78P260N
EM78P260N
Fig. 6-16 External Clock Input Circuit
In most applications, Pin OSCI and Pin OSCO can be connected with a crystal or
ceramic resonator to generate oscillation. Fig. 6-17 below depicts such a circuit. The
same applies to the HXT mode and the LXT mode.
ceramic resonator to generate oscillation. Fig. 6-17 below depicts such a circuit. The
same applies to the HXT mode and the LXT mode.
OSCI
EM78P259N
EM78P260N
EM78P260N
OSCO
Crystal
RS
C2
C1
Fig. 6-17 Crystal/Resonator Circuit
The following table provides the recommended values for C1 and C2. Since each
resonator has its own attribute, you should refer to the resonator specifications for the
appropriate values of C1 and C2. RS, a serial resistor, may be required for AT strip cut
crystal or low frequency mode.
resonator has its own attribute, you should refer to the resonator specifications for the
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)
455kHz 100~150 100~150
2.0 MHz
2.0 MHz
20~40
20~40
Ceramic Resonators
HXT
4.0 MHz
10~30
10~30
32.768kHz
25
15
100kHz
25
25
LXT
200kHz
25
25
455kHz 20~40 20~150
1.0 MHz
1.0 MHz
15~30
15~30
2.0 MHz
15
15
Crystal Oscillator
HXT
4.0 MHz
15
15