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HD404328 Datasheet, PDF (39/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER
HD404328 Series
Internal Oscillator Circuit
A block diagram of the internal oscillator circuit is shown in figure 22. As shown in table 21, crystal and
ceramic oscillators can be connected to OSC1 and OSC2, and a 32.768-kHz oscillator can be connected to
X1 and X2. The system oscillator can also be operated by an external clock. Bit 3 of the miscellaneous
register (MIS: $00C) must be set according to the frequency of the oscillator connected to OSC1 and OSC2.
Note: If the MIS register setting does not match the oscillator frequency, subsystems using 32-kHz
oscillation will malfunction. Set the system oscillator frequency to anything outside the range of
1.0 MHz to 1.6 MHz when using 32-kHz oscillation.
Miscellaneous register (MIS): $00C
3
2
1
0
Initial value: 0000,
R/W: W
tRC selection
R12/SO PMOS off
Setting for switching
the system oscillator’s
frequency
MIS
Bit 3
0
1
Figure 21 Miscellaneous Register
System Oscillator’s
Frequency
1.6 MHz to 4.5 MHz
0.4 MHz to 1.0 MHz
OSC2
OSC1
X1
X2
System
oscillator
Divide-by-8
circuit
Sub-system
oscillator
Divide-by-8
circuit
Timing
generator
circuit
Synch.
(tcyc)
Timing
generator
circuit
Synch.
(tsubcyc )
Mode
control
circuit
Figure 22 Internal Oscillator Circuit
System
clock
(øCPU)
System
clock
(øPER)
Time-base
clock
(ø CLK)
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