M306H7MG-XXXFP Datasheet, PDF (37/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
4. CLOCK GENERATION CIRCUIT
4.4.3 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 pins is VRAM or more, the internal RAM is
retained.
However, the peripheral functions clocked by external signals keep operating. The following interrupts can be
used to exit stop mode.
• NMI interrupt
• INT interrupt
• Timer A, Timer B interrupt (when counting external pulses in event counter mode)
• Serial I/O interrupt (when external clock is selected)
The internal oscillator circuit of expansion function (Data acquisition / humming function) stops oscillation
when expansion register XTAL_VCO, PDC_VCO_ON, VPS_VCO_ON = "L".
• 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) and the CM15 bit of
CM1 register is set to “1” (main clock oscillator circuit drive capability high).
• Pin Status in Stop Mode
Table 4.4 lists pin status during stop mode
• Exiting Stop Mode
The microcomputer is moved out of stop mode by a hardware reset, NMI interrupt or peripheral function
interrupt.
If the microcomputer is to be moved out of stop mode by a hardware reset or NMI interrupt, 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 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 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 or NMI interrupt 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 sub clock: sub clock
If the CPU clock before entering stop mode was derived from the main clock: main clock divide-by-8
Rev.2.10 Oct 25, 2006 Page 37 of 326
REJ03B0152-0210