Section 18 Clock Pulse Generator
Rev. 3.00 Mar. 14, 2006 Page 661 of 804
REJ09B0104-0300
Section 18 Clock Pulse Generator
This LSI has an on-chip clock pulse generator (CPG) that generates the system clock (I
φ
),
peripheral module clock (P
φ
), and external clock (B
φ
).
The clock pulse generator consists of an oscillator, PLL (Phase Locked Loop) circuit, and divider.
Figure 18.1 shows a block diagram of the clock pulse generator.
Clock frequencies can be changed by the PLL circuit and divider in the CPG. Changing the
system clock control register (SCKCR) setting by software can change the clock frequencies.
This LSI supports three types of clocks: a system clock provided to the CPU and bus masters, a
peripheral module clock provided to the peripheral modules, and an external clock provided to the
external bus. These clocks can be specified independently. Note, however, that the frequencies of
the peripheral clock and external clock are lower than that of the system clock.
EXTAL
XTAL
PLL
circuit
Oscillator
Selector
System clock (I
φ
)
(to the CPU and
bus masters)
Peripheral module
clock (P
φ
)
(to peripheral modules)
External bus clock (B
φ
)
(to the B
φ
pin)
ICK2 to ICK0
SCKCR
PCK2 to PCK0
Divider
(1/1,
1/2,
1/4,
and 1/8)
BCK2 to BCK0
EXTAL
×
8
1/1
1/2
1/4
1/8
Selector
SCKCR
1/1
1/2
1/4
1/8
Selector
SCKCR
1/1
1/2
1/4
1/8
Figure 18.1 Block Diagram of Clock Pulse Generator
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Содержание H8SX series
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