NEC UPD789026 Series, User Manual

Page: 85 / 213

User's Manual U11919EJ3V0UM00
85
CHAPTER 5 CLOCK GENERATION CIRCUIT
5.1 Function of Clock Generation Circuit
The clock generation circuit generates the clock to be supplied to the CPU and peripheral hardware. The system
clock oscillator consists of the following type.
•
System clock oscillator
This circuit oscillates at frequencies of 1.0 to 5.0 MHz. Oscillation can be stopped by executing the STOP
instruction.
5.2 Configuration of Clock Generation Circuit
The clock generation circuit consists of the following hardware.
Table 5-1. Configuration of Clock Generation Circuit
Item Configuration
Control register Processor clock control register (PCC)
Oscillator System clock oscillator
Figure 5-1. Block Diagram of Clock Generation Circuit
X1
X2 f
X
Prescaler
2
2
f
X
Selector
PCC1
Internal Bus
Processor Clock Control Register (PCC)
Prescaler
Standby
Control
Circuit
Wait Control
Circuit
CPU Clock (f
CPU
)
Clock to Peripheral
Hardware
System Clock
Oscillator
STOP
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