User’s Manual U15331EJ4V1UD 95
CHAPTER 5 CLOCK GENERATOR
5.1 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 used.
• Main system clock oscillator
This circuit oscillates at 1.0 to 5.0 MHz. Oscillation can be stopped by executing the STOP instruction or setting
the processor clock control register (PCC).
• Subsystem clock oscillator
This circuit oscillates at 32.768 kHz. Oscillation can be stopped by the suboscillation mode register (SCKM).
Also, a circuit to multiply the subsystem clock by 4 can be used by setting a mask option or the subclock
selection register (SSCK).
5.2 Clock Generator Configuration
The clock generator includes the following hardware.
Table 5-1. Configuration of Clock Generator
Item Configuration
Control registers Processor clock control register (PCC)
Subclock oscillation mode register (SCKM)
Subclock control register (CSS)
Subclock selection register (SSCK) (
µ
PD78F9488, 78F9489 only)
Oscillators Main system clock oscillator
Subsystem clock oscillator