M16C29 Datasheet, PDF (86/499 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/Tiny SERIES

M16C/29 Group
7. Clock Generation Circuit
7.6.3 Stop Mode
In stop mode, all oscillator circuits are turned off, so are the CPU clock and the peripheral function clocks.
Therefore, the CPU and the peripheral functions clocked by these clocks stop operating. The least amount of
power is consumed in this mode. If the voltage applied to Vcc pin is VRAM or more, the internal RAM is
retained. When applying 2.7 or less voltage to Vcc pin, make sure Vcc≥VRAM.
However, the peripheral functions clocked by external signals keep operating. The following interrupts can
be used to exit stop mode.
______
• NMI interrupt
• Key interrupt
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• INT interrupt
• Timer A, Timer B interrupt (when counting external pulses in event counter mode)
• Serial I/O interrupt (when external clock is selected)
• Low voltage detection interrup (refer to "Low Voltage Detection Interrupt" for an operating
condition)
• CAN0 Wake_up interrupt (in CAN sleep mode)
7.6.3.1 Entering Stop Mode
The MCU is placed into stop mode by setting the CM10 bit in the CM1 register to 1 (all clocks turned off).
At the same time, the CM06 bit in the CM0 register is set to 1 (divide-by-8 mode) and the CM15 bit in the
CM10 register is set to 1 (main clock oscillator circuit drive capability high).
Before entering stop mode, set the CM20 bit to 0 (oscillation stop, re-oscillation detection function dis-
able).
Also, if the CM11 bit is 1 (PLL clock for the CPU clock source), set the CM11 bit to 0 (main clock for the
CPU clock source) and the PLC07 bit to 0 (PLL turned off) before entering stop mode.
7.6.3.2 Pin Status during Stop Mode
The I/O pins retain their status held just prior to entering stop mode.
7.6.3.3 Exiting Stop Mode
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The MCU is moved out of stop mode by a hardware reset, NMI interrupt or peripheral function interrupt.
______
If the MCU is to be moved out of stop mode by a hardware reset or NMI interrupt, set the peripheral
function interrupt priority bits ILVL2 to ILVL0 to 0002 (interrupts disable) before setting the CM10 bit to 1.
If the MCU is to be moved out of stop mode by a peripheral function interrupt, set up the following before
setting the CM10 bit to 1.
1. In bits ILVL2 to ILVL0 of the interrupt control register, set the interrupt priority level of the peripheral
function interrupt to be used to exit stop mode.
Also, for all of the peripheral function interrupts not used to exit stop mode, set bits ILVL2 to ILVL0 to
0002.
2. Set the I flag to 1.
3. Enable the peripheral function whose interrupt is to be used to exit stop mode.
In this case, when an interrupt request is generated and the CPU clock is thereby turned on, an
interrupt service routine is executed.
______
Which CPU clock will be used after exiting stop mode by a peripheral function or NMI interrupt is deter-
mined by the CPU clock that was on when the MCU was placed into stop mode as follows:
If the CPU clock before entering stop mode was derived from the sub clock: sub clock
If the CPU clock before entering stop mode was derived from the main clock: main clock divide-by-8
If the CPU clock before entering stop mode was derived from the on-chip oscillator clock: on-chip oscil-
lator clock divide-by-8
Rev. 1.12 Mar.30, 2007
REJ09B0101-0112
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