EM78P221/2N
8-Bit Microcontroller with OTP ROM
42 •
Product Specification (V1.0) 10.19.2007
(This specification is subject to change without further notice)
In most applications, Pin OSCI and Pin OSCO can be connected with a crystal or
ceramic resonator to generate oscillation. Fig. 6-13 below depicts such a circuit. The
same applies to the HXT 1, 2 modes and the LXT 1, 2 modes.
OSCI
OSCO
C1
C2
Crystal
RS
Fig. 6-13 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. Fig 6-13-1 is a recommended PCB layout. When the
system works in Crystal mode (16MHz), a 10KΩ is connected between OSCI and
OSCO.
Capacitor selection guide for crystal oscillator or ceramic resonators:
Oscillator Type Frequency Mode Frequency C1 (pF) C2 (pF)
100kHz 67pF 67pF
200kHz 30pF 30pF
455kHz 30pF 30pF
LXT
(100K~1MHz)
1MHz 30pF 30pF
1.0 MHz 30pF 30pF
2.0 MHz 30pF 30pF
Ceramic Resonators
HXT
(1M~6MHz)
4.0 MHz 30pF 30pF
LXT2 (32.768kHz) 32.768kHz 20pF 20pF
100kHz 67pF 67pF
200kHz 30pF 30pF
455kHz 30pF 30pF
LXT1
(100K~1MHz)
1MHz 30pF 30pF
455kHz 30pF 30pF
1.0 MHz 30pF 30pF
2.0 MHz 30pF 30pF
4.0 MHz 30pF 30pF
HXT2
(1~6MHz)
6.0 MHz 30pF 30pF
6.0 MHz 30pF 30pF
8.0 MHz 30pF 30pF
12.0 MHz 30pF 30pF
Crystal Oscillator
HXT1
(6~16MHz)
16.0 MHz 15pF 15pF
