Section 4 Clock Pulse Generators
Rev. 7.00 Mar 10, 2005 page 111 of 652
REJ09B0042-0700
4.3 Subclock Generator
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 4.8. Follow the same precautions as noted under 3. notes on board
design for the system clock in section 4.2.
Note that only operation at 32.768 kHz is guaranteed on the H8/38124 Group.
X
X
C
1
C
2
1
2
C = C = 15 pF (typ.)
12
Frequency
38.4 kHz
32.768 kHz
Crystal oscillator
Seiko Instruments Inc.
Nihon Denpa Kogyo
Products Name
VTC-200
MX73P
Figure 4.8 Typical Connection to 32.768 kHz/38.4 kHz Crystal Oscillator (Subclock)
Figure 4.9 shows the equivalent circuit of the 32.768 kHz/38.4 kHz crystal oscillator.
C
S
C
0
LR
S
X
1
X
2
C = 1.5 pF typ
R = 14 k typ
f = 32.768 kHz/38.4 kHz
0
S
W
Ω
S
Figure 4.9 Equivalent Circuit of 32.768 kHz/38.4 kHz Crystal Oscillator
Pin Connection when Not Using Subclock
When the subclock is not used, connect pin X
1
to GND and leave pin X
2
open, as shown in figure
4.10.
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