Rev. 1.0, 03/01, page 61 of 280
Section 5 Clock Pulse Generators
Clock oscillator circuitry (CPG: clock pulse generator) is provided on-chip, including a system
clock pulse generator. The system clock pulse generator consists of a system clock oscillator, a
duty correction circuit, and system clock dividers.
Figure 5-1 shows a block diagram of the clock pulse generators.
System
clock
oscillator
Duty
correction
circuit
System
clock
divider
Prescaler S
(13 bits)
OSC
1
OSC
2
System clock pulse generator
ø
OSC
(f
OSC
)
ø
OSC
(f
OSC
)
ø/2
to
ø/8192
ø
ø
OSC
/8
ø
OSC
ø
OSC
/16
ø
OSC
/32
ø
OSC
/64
Figure 5-1 Block Diagram of Clock Pulse Generators
The basic clock signals that drive the CPU and on-chip peripheral modules are ø.
The system clock is divided into ø/8192 to ø/2 by prescaler S and they are supplied to respective
peripheral modules.
5.1
System Clock Generator
Clock pulses can be supplied to the system clock divider either by connecting a crystal or ceramic
oscillator, or by providing external clock input.
5.1.1
Connecting a Crystal Oscillator
Figure 5-2 shows a typical method of connecting a crystal oscillator. An AT-cut parallel-
resonance crystal resonator should be used. Figure 5-3 shows the equivalent circuit of a crystal
oscillator. An oscillator having the characteristics given in table 5-1 should be used.
1
2
C
1
C
2
OSC
OSC
C = C = 12 pF ±20%
1
2
Figure 5-2 Typical Connection to Crystal Oscillator
Содержание H8/3670F-ZTAT HD64F3670
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