Clock Pulse Generators; Overview; Block Diagram; System Clock And Subclock - Hitachi H8/3937 Series Hardware Manual

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.
OSC
1 System clock
oscillator
OSC
2
System clock pulse generator
DX
1
Subclock
DX oscillator
2
Subclock pulse generator
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 ø and ø
the clock signals have names: ø is the system clock, ø
clock, ø is the watch clock, and ø
w
The clock signals available for use by peripheral modules are ø/2, ø/4, ø/8, ø/16, ø/32, ø/64, ø/128,
ø/256, ø/512, ø/1024, ø/2048, ø/4096, ø/8192, ø
and ø . The clock requirements differ from one module to another.
DEC
Section 4 Clock Pulse Generators
ø
OSC
System clock
divider (1/2)
(f )
OSC
Subclock Subclock
ø
W
oscillator divider
(f )
(1/2) (1/2, 1/4, 1/8)
W
is the decoder clock.
DEC
ø /2
OSC
ø
OSC
ø
System
OSC
clock
ø
OSC
divider
ø
OSC
ø /2
W
ø /4
W
ø /8
W
is the subclock, ø
SUB
, ø /2, ø /4, ø /8, ø
W W W W
/128
ø
/64
/32
Prescaler S
(13 bits)
/16
ø
SUB
Prescaler W
(5 bits)
. Five of
SUB
is the oscillator
OSC
/16, ø /32, ø /64, ø
W W W
ø/2
to
ø/8192
ø
DEC
ø
W
ø /2
W
ø /4
W
ø /8
W
to
ø /128
W
/128,
W
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