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MB95630H Series
3.4
Clock Modes
There are five clock modes: main clock mode, subclock mode, main CR clock
mode, main CR PLL clock mode, and sub-CR clock mode. Mode switching
occurs according to the settings in the system clock control register (SYCC).
■ Operations in Main Clock Mode
In main clock mode, the main clock is used as the machine clock for the CPU and peripheral
functions.
The time-base timer operates using the main clock.
The watch prescaler operates using the subclock or the sub-CR clock.
While the device is operating in main clock mode, it can be set to transit to one of the
following standby mode: sleep mode, stop mode, or time-base timer mode.
After a reset, the device always enters main CR clock mode regardless of the clock mode used
before that reset.
■ Operations in Subclock Mode
In subclock mode, main clock oscillation is stopped* and the subclock is used as the machine
clock for the CPU and peripheral functions. In this mode, the time-base timer stops as it
requires the main clock for operation.
While the device is operating in subclock mode, it can be set to transit to one of the following
standby mode: sleep mode, stop mode, or watch mode.
■ Operations in Main CR Clock Mode or Main CR PLL Clock Mode
In main CR clock mode or main CR PLL clock mode, the main CR clock or the main CR PLL
clock is used as the machine clock for the CPU and peripheral functions. The time-base timer
and the watchdog timer operate using the main CR clock or the main CR PLL clock.
The watch prescaler operates using the subclock or the sub-CR clock.
While the device is operating in main CR clock mode or the main CR PLL clock mode, it can
be set to transit to one of the following standby mode: sleep mode, stop mode, or time-base
timer mode.
■ Operations in Sub-CR Clock Mode
In sub-CR clock mode, main clock oscillation is stopped* and the sub-CR clock is used as the
machine clock for the CPU and peripheral functions. In this mode, the time-base timer stops as
it requires the main clock for operation. The watch prescaler operates using the sub-CR clock.
While the device is operating in sub-CR clock mode, it can be set to transit to one of the
following standby mode: sleep mode, stop mode, or watch mode.
*: The oscillation of the main clock, main CR clock, or main CR PLL clock is automatically disabled
(writing "0" to SYCC2:MOSCE, SYCC2:MCRE or PLLC:MPEN respectively) when the clock mode
transits from main clock mode, main CR clock mode or main CR PLL clock mode to subclock mode or
sub-CR clock mode. In subclock mode or sub-CR clock mode, writing "1" to SYCC2:MOSCE,
SYCC2:MCRE or PLLC:MPEN cannot enable the main clock, the main CR clock, or the main CR
PLL clock respectively.
MN702-00009-1v0-E
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER 3 CLOCK CONTROLLER
3.4 Clock Modes
37
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