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Figure 4.8 shows the equivalent circuit of the 32.768-kHz crystal oscillator.
X
1
Figure 4.8 Equivalent Circuit of 32.768-kHz Crystal Oscillator
Inputting an External Clock
• Circuit configuration
An external clock is input to the X
An example of the connection in this case is shown in figure 4.9.
Figure 4.9 Example of Connection when Inputting an External Clock
• External clock
Input a square waveform to the X1 pin. When using the CPU, timer A, timer C*, or an LCD,
with a subclock (φw) clock selected, do not stop the clock supply to the X
Note: * This is a function of the H8/3857 Group only, and is not provided in the H8/3854
Group.
C
S
L
S
C
0
pin. The X
1
X
1
X
2
R
S
C = 1.5 pF typ
0
R = 14 kΩ typ
S
f
= 32.768 kHz
W
Crystal oscillator:
MX38T
(Nihon Denpa Kogyo)
pin should be left open.
2
External clock input
Open
Rev.3.00 Jul. 19, 2007 page 97 of 532
4. Clock Pulse Generators
X
2
pin.
1
REJ09B0397-0300
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