M16C6S_09 Datasheet, PDF (39/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Clock Generation Circuit
(3) Stop Mode
In stop mode, all the M16C core's internal 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.
However, the peripheral functions clocked by external signals keep operating. The following interrupts
can be used to exit stop mode.
______
• INT interrupt
• Timer A, interrupt (when counting external pulses in event counter mode)
• Serial I/O interrupt (when external clock is selected)
• Entering Stop Mode
The microcomputer is placed into stop mode by setting the CM10 bit of CM1 register to “1” (all clocks
turned off). At the same time, the CM06 bit of CM0 register is set to “1” (divide-by-8 mode).
Before entering stop mode, set the CM20 bit to “0” (oscillation stop, re-oscillation detection function
disable).
• Pin Status in Stop Mode
Table 1.7.5 lists pin status during stop mode
• Exiting Stop Mode
The microcomputer is moved out of stop mode by a hardware reset or peripheral function interrupt.
If the microcomputer is to be moved out of stop mode by a hardware reset, set the peripheral function
interrupt priority ILVL2 to ILVL0 bits to “0002” (interrupts disable) before setting the CM10 bit to “1”.
If the microcomputer 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 the ILVL2 to ILVL0 bits of interrupt control register, set the interrupt priority level of the periph-
eral function interrupt to be used to exit stop mode.
Also, for all of the peripheral function interrupts not used to exit stop mode, set the ILVL2 to ILVL0
bits 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 is determined by the
CPU clock that was on when the microcomputer was placed into stop mode as follows:
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
Oscillator clock divide-by-8
Rev.5.01 Dec 10, 2009 page 39 of 201
REJ03B0014-0501