em78f644nso28s ELAN Microelectronics Corp, em78f644nso28s Datasheet - Page 161

• Manufacturer Part Number: em78f644nso28s
• Description: Flash Series 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.0) 05.05.2010
(This specification is subject to change without further notice)
In LXT1, LXT2, XT, HXT, and ERC modes, OSCI and OSCO are used. These pins
can’t be used as normal I/O pin. In IRC mode, P55 is used as normal I/O pin
6.15.2 Crystal Oscillator/Ceramic Resonators (XTAL)
EM78F64x/54xN can be driven by an external clock signal through the OSCI pin as
illustrated below.
In most applications, Pins OSCI and OSCO are connected with a crystal or ceramic
resonator to generate oscillation as depicted in the circuit diagram below. The same
thing applies under HXT or LXT mode. The following table (next page) provides the
recommended values for C1 and C2. Since each resonator has its own attribute, you
should refer to the pertinent resonator specification for appropriate C1/C2 values. RS,
a serial resistor, may be necessary for AT strip cut crystal or low frequency mode.
Summary of Maximum Operating Speed:
1. Frequency range of HXT mode is 20MHz ~ 6MHz.
2. Frequency range of XT mode is 6MHz ~ 1MHz.
3. Frequency range of LXT1 mode is 1MHz ~ 100kHz.
4. Frequency range of XT mode is 32kHz.
Two cycles with two clocks
Conditions
Figure 6-27a External Clock Input Circuit
Figure 6-27b Crystal/Resonator Circuit
EM78F648/644/642/641/548/544/542/541N
NOTE
VDD
2.5
3.0
5.0
Fxt Max.(MHz)
8-Bit Microcontroller
20.0
4.0
8.0
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