Datasheet

Section 4 Clock Pulse Generators
Rev. 6.00 Aug 04, 2006 page 119 of 680
REJ09B0145-0600
Section 4 Clock Pulse Generators
4.1 Overview
Clock oscillator circuitry (CPG: clock pulse generator) is provided on-chip, including both a
system clock pulse generator and a subclock pulse generator. The system clock pulse generator
consists of a system clock oscillator and system clock dividers. The subclock pulse generator
consists of a subclock oscillator circuit and a subclock divider.
4.1.1 Block Diagram
Figure 4.1 shows a block diagram of the clock pulse generators.
System clock
oscillator
System clock
divider (1/2)
Subclock
oscillator
Subclock
divider
(1/2, 1/4, 1/8)
System
clock
divider
System clock pulse generator
Subclock pulse generator
Note: * H8/38347 Group and H8/38447 Group only.
Prescaler S
(13 bits)
Prescaler W
(5 bits)
OSC
OSC
1
2
X
X
EXCL*
1
2
φ
OSC
(f )
OSC
φ
W
φ
W
(f )
W
φ
/2
OSC
φ
/2
W
φ
/8
W
φ
SUB
φ
/2
to
φ
/8192
φ
/2
W
φ
/4
W
φ
/8
to
φ
/128
W
W
φ
φ
OSC
/128
φ
OSC
/64
φ
OSC
/32
φ
OSC
/16
φ
/4
W
Figure 4.1 Block Diagram of Clock Pulse Generators
4.1.2 System Clock and Subclock
The basic clock signals that drive the CPU and on-chip peripheral modules are φ and φ
SUB
. Four
of the clock signals have names: φ is the system clock, φ
SUB
is the subclock, φ
OSC
is the oscillator
clock, and φ
W
is the watch clock.
The clock signals available for use by peripheral modules are φ/2, φ/4, φ/8, φ/16, φ/32, φ/64,
φ/128, φ/256, φ/512, φ/1024, φ/2048, φ/4096, φ/8192, φ
W
, φ
W
/2, φ
W
/4, φ
W
/8, φ
W
/16, φ
W
/32, φ
W
/64,
and φ
W
/128. The clock requirements differ from one module to another.