
R8C/3GM Group
9. Clock Generation Circuit
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
9.7.2
Wait Mode
Since the CPU clock stops in wait mode, the CPU operating with the CPU clock and the watchdog timer when
count source protection mode is disabled stop. Since the XIN clock, XCIN clock, and on-chip oscillator clock
do not stop, the peripheral functions using these clocks continue operating.
9.7.2.1
Peripheral Function Clock Stop Function
If the CM02 bit is set to 1 (peripheral function clock stops in wait mode), the f1, f2, f4, f8, and f32 clocks stop
in wait mode. This reduces power consumption.
9.7.2.2
Entering Wait Mode
The MCU enters wait mode by executing the WAIT instruction or setting the CM30 bit in the CM3 register to 1
(MCU enters wait mode).
When the OCD2 bit in the OCD register is set to 1 (on-chip oscillator selected as system clock), set the OCD1
bit in the OCD register to 0 (oscillation stop detection interrupt disabled) before executing the WAIT
instruction or setting the CM30 bit in the CM3 register to 1(MCU enters wait mode).
If the MCU enters wait mode while the OCD1 bit is set to 1 (oscillation stop detection interrupt enabled),
current consumption is not reduced because the CPU clock does not stop.
When entering wait mode, set the FMR01 bit in the FMR0 register to 0 (CPU rewrite mode disabled) and the
FMR27 bit to 0 (low-current-consumption read mode disabled) before entering the mode.
Do not enter wait mode while the FMR01 bit is 1 (CPU rewrite mode enabled) or the FMR27 bit is 1
(lowcurrent-consumption read mode enabled).
To enter wait mode by setting the CM30 bit to 1, set the I flag to 0 (maskable interrupt disabled). To enter wait
mode using the WAIT instruction, set the I flag to 1 (maskable interrupt enabled).
9.7.2.3
Reducing Internal Power Using VCA20 Bit
When the MCU enters wait mode using low-speed clock mode or low-speed on-chip oscillator mode, internal
power consumption can be reduced using the VCA20 bit in the VCA2 register. To enable internal power
9.7.2.4
Pin Status in Wait Mode
The I/O ports retain the status immediately before the MCU enters wait mode.