NEC mPD780851, Preliminary User'S Manual

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Preliminary User’s Manual U14581EJ3V0UM00
CHAPTER 5 CLOCK GENERATOR
5.1 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 4.00 to 8.38 MHz. Oscillation can be stopped by executing the STOP
instruction.
Figure 5-1 shows clock generator block diagram.
Figure 5-1. 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
controller
Selector
STOP
PCC2 PCC1
3
PCC0
Processor clock control register (PCC) Oscillator mode register (OSCM)
Internal bus
5.2 Clock Generator Configuration
The clock generator consists of the following hardware.
Table 5-1. Clock Generator Configuration
Item Configuration
Control register Processor clock control register (PCC)
Oscillator mode register (OSCM)
Note
Oscillator Main system clock oscillator
Note
µ
PD780851(A), 780852(A) only