CHAPTER 5 CLOCK GENERATION CIRCUIT
User's Manual U11919EJ3V0UM00
87
5.4 System Clock Oscillation Circuits
5.4.1 System clock oscillation circuit
The system clock oscillation circuit is oscillated by the crystal or ceramic resonator (5.0 MHz TYP.) connected
across the X1 and X2 pins.
An external clock can also be input to the circuit. In this case, input the clock signal to the X1 pin, and input the
reversed signal to the X2 pin.
Figure 5-3 shows the external circuit of the system clock oscillation circuit.
Figure 5-3. External Circuit of System Clock Oscillation Circuit
(a) Crystal or ceramic oscillation
(b) External clock
V
SS0
, V
SS1
X1
X2
Crystal
or
Ceramic Resonator
External
Clock
X1
X2
Caution
When using the system clock oscillator circuit, to avoid influence of wiring capacity, etc., wire
the portion enclosed by the broken line in Figure 5-3 as follows:
••••
Keep the wiring length as short as possible.
••••
Do not cross the wiring with any other signal lines. Do not route the wiring in the vicinity of a
line through which a high alternating current flows.
••••
Always keep the ground of the capacitor of the oscillation circuit at the same potential as V
SS
.
Do not ground the capacitor to a ground pattern through which a high current flows.
••••
Do not extract signals from the oscillation circuit.
Figure 5-4 shows incorrect examples of resonator connection.
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Содержание UPD789026 Series
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