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