91
4.3
Subclock Generator
1. Connecting a 32.768-kHz/38.4 kHz crystal oscillator
Clock pulses can be supplied to the subclock divider by connecting a 32.768-kHz/38.4 kHz crystal
oscillator, as shown in figure 4.7. Follow the same precautions as noted under 3. notes on board
design for the system clock in 4.2.
X
X
C
1
C
2
1
2
C = C = 15 pF (typ.)
1
2
Oscillation
frequency
32.768 kHz
38.4 kHz
Manufacturer
Nihon Denpa Kogyo
Seiko Instrument Inc.
Products Name
MX73P
VTC-200
Figure 4.7 Typical Connection to 32.768-kHz/38.4 kHz Crystal Oscillator (Subclock)
Figure 4.8 shows the equivalent circuit of the 32.768-kHz/38.4 kHz crystal oscillator.
C
S
C
0
L
R
S
X
1
X
2
C = 1.5 pF typ
R = 14 k typ
f = 32.768 kHz/38.4kHz
0
S
W
Ω
S
Figure 4.8 Equivalent Circuit of 32.768-kHz/38.4 kHz Crystal Oscillator