Clock Modes - Fujitsu F2MC-8FX Hardware Manual

6.7

Clock Modes

The clock modes available are: main clock mode, subclock mode and main PLL clock
mode. Mode switching takes place according to the settings in the system clock control
register (SYCC).
Subclock mode is not supported by single system clock product.
Operations in Main Clock Mode
Main clock mode uses the main clock as the machine clock for the CPU and peripheral resources.
The timebase timer operates with the main clock.
The watch prescaler and watch counter operate with the subclock (on two-system clock product).
If you set standby mode during operation in main clock mode, the device can enter sleep mode, stop mode,
or timebase timer mode.
After a reset, main clock mode is always set regardless of the clock mode used before the reset.
Operations in Subclock Mode (on Two-system Clock Product)
Subclock mode uses the subclock as the machine clock for the CPU and peripheral resources with main
clock oscillation stopped. In this mode, the timebase timer remains stopped as it requires the main clock for
operation.
If you set standby mode during operation in subclock mode, the device can enter sleep mode, stop mode, or
watch mode.
Operations in Main PLL Clock Mode
Main PLL clock mode uses the main PLL clock as the machine clock for the CPU and peripheral resources.
The timebase timer and watchdog timer operate with the main clock.
The watch prescaler and watch counter operate with the subclock (on two-system clock product).
If you set standby mode during operation in main PLL clock mode, the device can enter sleep mode, stop
mode, or timebase timer mode.
CHAPTER 6 CLOCK CONTROLLER
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