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19.2 Oscillator Circuit
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Clock pulses can be supplied by connecting a crystal resonator, or by input of an external clock
signal.
19.2.1 Connecting a Crystal Resonator
Circuit Configuration: A crystal resonator can be connected as in the example in figure 19-2.
The damping resistance Rd should be selected according to table 19-1. An AT-cut parallel-
resonance crystal should be used.
EXTAL
XTAL
Figure 19-2 Connection of Crystal Resonator (Example)
Table 19-1 Damping Resistance Value
Damping Resistance
Value
2
Rd
For products
1 k
listed below *
(Ω)
HD64F3048
1 k
Note: A crystal resonator between 2 MHz and 18 MHz (between 2 MHz and 16 MHz for the flash
memory version) can be used. If the chip is to be operated at less than 2 MHz, the on-chip
frequency divider should be used. (A crystal resonator of less than 2 MHz cannot be used.)
* HD6473048, HD6433048, HD6433047, HD6433045, HD6433044
Crystal Resonator: Figure 19-3 shows an equivalent circuit of the crystal resonator. The crystal
resonator should have the characteristics listed in table 19-2.
C
L1
Rd
C
L2
2 < f ≤ 4
4 < f ≤ 8
8 < f ≤ 10
500
200
0
1 k
500
200
634
C
= C
= 10 pF to 22 pF
L1
L2
Frequency f (MHz)
10 < f ≤ 13 13 < f ≤ 16 16 < f ≤ 18
0
0
100
0
0
—
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