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| HD404849 Datasheet, PDF (43/125 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer | |||
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HD404849 Series
Table 22 Oscillator Circuit Examples
External clock
operation
Circuit Configuration
External
oscillator
OSC 1
Circuit Constants
Open
OSC2
Ceramic
oscillator
(OSC1, OSC2)
Crystal oscillator
(OSC1,OSC2)
C1
OSC1
Ceramic
oscillator
Rf
C2
GND
OSC2
C1
Crystal
oscillator
GND
C2
L
OSC1
Rf
OSC2
CS RS
Ceramic oscillator:
CSA4.00MG (Murata)
Rf = 1 M⦠± 20%
C1 = C2 = 30 pF ± 20%
Rf = 1 M⦠± 20%
C1 = C2 = 10 to 22 pF ± 20%
Equivalent circuit of crystal
oscillator shown at left.
C0: 7 pF max
RS: 100 ⦠max
Crystal oscillator
(X1, X2)
OSC1
C0
C1
X1
Crystal
oscillator
C2
GND
X2
L CS RS
OSC2
Crystal: 32.768 kHz: MX38T
(Nippon Denpa)
C1 = C2 = 20 pF ± 20%
RS: 14 kâ¦
C0: 1.5 pF
X1
X2
C0
Notes: 1. Circuit constants differ by the different types of crystal oscillators and ceramic oscillators, and
with the stray capacitance of the board, so consult the manufacturer of the oscillator to determine
the circuit parameters.
2. The wiring between the OSC1 and OSC2 pins (X1 and X2 pins) and the other elements should be
as short as possible, and must not cross other wiring. Refer to figure 27.
3. If not using a 32.768-kHz crystal oscillator, fix the X1 pin to VCC and leave the X2 pin open.
43
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