NEC uPD78P078 - Manual (Page 165)

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CHAPTER 7 CLOCK GENERATOR
7.1 Clock Generator Functions
The clock generator generates the clock to be supplied to the CPU and peripheral hardware. The following two
types of system clock oscillators are available.
(1) Main system clock oscillator
This circuit oscillates at frequencies of 1 to 5.0 MHz. Oscillation can be stopped by executing the STOP
instruction or setting the processor clock control register (PCC).
(2) Subsystem clock oscillator
The circuit oscillates at a frequency of 32.768 kHz. Oscillation cannot be stopped. If the subsystem clock
oscillator is not used, not using the internal feedback resistance can be set by the processor clock control
register (PCC). This enables to decrease power consumption in the STOP mode.