89
CHAPTER 6 CLOCK GENERATOR
6.1 Clock Generator Functions
The clock generator generates the clock to be supplied to the CPU and peripheral hardware.
• Main system clock oscillator
This circuit oscillates at frequencies of 4.19 to 8.38 MHz. Oscillation can be stopped by executing the STOP
instruction or setting the processor clock control register (PCC).
6.2 Clock Generator Configuration
The clock generator consists of the following hardware.
Table 6-1. Clock Generator Configuration
Item
Configuration
Control register
Processor clock control register (PCC)
Oscillator mode register (OSCM)
Note
Oscillator
Main system clock oscillator
Note
µ
PD780973(A) only
Figure 6-1. Clock Generator Block Diagram
X1
X2
Main system
clock oscillator
HALFOSC
f
X
Prescaler
f
X
2
f
X
2
2
f
X
2
3
f
X
2
4
Prescaler
Clock to
peripheral
hardware
CPU clock
(f
CPU
)
Standby
control
circuit
Selector
STOP
PCC2 PCC1
3
PCC0
Processor clock control register
Oscillator mode register
Internal bus
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