User guide

14
SmartBook for Renesas R8C/Tiny Microcontrollers
www.MightyMicons.com
If the main clock stops oscillating when the OCD1 to OCD0
bits in the OCD register are set to “11” (Oscillation Stop
Detection function enabled), the low-speed on-chip oscillator
automatically starts operating, supplying the necessary clock
to the microcomputer. The frequency of the low-speed on-
chip oscillator varies depending on the supply voltage and the
operating ambient temperature. The applications must be
designed with sufficient margin to accommodate the frequency range.
2.5 High Speed On Chip Oscillator Clock:
The clock derived from high-speed on-chip oscillator is used as the clock source
for the CPU clock, peripheral function clocks, fRING, fRING128, and fRING-fast.
After reset, the on-chip oscillator clock derived from high-speed on-chip oscillator
is disabled. The oscillation is started by setting the HR00 bit in the HR0 register
to “1” (high-speed on-chip oscillator on). The HR1 register can adjust the frequency
of this clock source.
2.6 Power Control Modes:
The R8C/Tiny family devices come with a versatile built in clock generating
mechanism that gives a range of clock sources to feed both the CPU and different
on chip peripheral functions. It also supports the usage of an external clock
source. Using these clock selecting options, the microcontrollers has the facility
to implement application specific power conserving tasks. The Micons deliver
more processing power with high speed clock sources. When the operating speed
is reduced, the power consumption also comes down significantly. These facilities
are much sought-after in power sensitive applications.
The R8C/Tiny devices have these power control modes: Normal mode, Wait mode
and Stop mode. The normal mode has its own operating modes: High speed
mode, Medium speed mode and High/Low speed on chip oscillator modes.
As you can recall from the pervious discussion on clock generating mechanism,
the chip operating system clock can get its clock from either external main clock
or from the internal ring oscillators. The CPU and the peripheral functions can get
the undivided system clock or one of the many divided clock options through
different clock dividers.
D
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t
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4
D
e
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n
The Micons deliver
more processing
power with high
speed clock
sources.
When the operating speed is re-
duced, the power consump-
tion also comes down
significantly.