HD404374 Datasheet, PDF (48/161 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip A/D Converter

HD404374/HD404384/HD404389/HD404082/HD404084 Series
Stop mode:
In stop mode, all MCU function stop except that states prior to entry into stop mode are retained. This
mode thus has the lowest power consumption of all operating mode.
In stop mode, the OSC₁ and OSC₂ oscillators stop. Bit 3 (SSR3) of the system clock select register (SSR:
$004) (figure 22) can be used to select the active (= 0) or stopped (= 1) state for the X1 and X2 oscillators.
The MCU is switched to stop mode by executing a STOP instruction while bit 3 (TMA3) of timer mode
register A (TMA: $00F) (figure 33) is cleared to 0 in active mode.
Stop
mode
is
cleared
by
RESET
or
WU
0
input. When stop mode is cleared by RESET, the RESET signal should be input for at least the oscillation
settling time (tRC) (see "AC Characteristics") shown in figure 13. Then, the MCU is initialized and starts
instruction execution from the start (address 0) of the program (IE = 0, IMWU = 0). If IE is set before
entering stop mode (IE = 1, IMWU = 0), wakeup interrupt handling is executed after the transition to active
mode.
When
the
MCU
detects
a
falling
edge
at
WU
0
in
stop
mode,
it
automatically
waits
for
the
oscillation
settling time, then switches to active mode. After the transition to active mode, the MCU resumes program
execution from the instruction following the STOP instruction.
If stop mode is cleared by wakeup input, RAM data and registers retain their values prior to entering stop
mode.
Oscillator
Stop mode
Internal clock
STOP instruction executed
tres
(At least oscillation settling time (tRC))
Figure 13 Timing Chart for Clearing Stop Mode by RESET Input
Note: If stop mode is cleared by wakeup input when an external clock is used as the system clock
(OSC1), the subclock should not be stopped in stop mode.
Watch mode ( Applies to HD404374 Series) :
In watch mode, the realtime clock function (timer A) and LCD function using the X1 and X2 oscillators
operate, but other functions stop. This mode thus has the second lowest power consumption after stop
mode, and is useful for performing realtime clock display only.
In watch mode, the OSC₁ and OSC₂ oscillators stop but the X1 and X2 oscillators continue to operate.
The MCU is switched to watch mode by executing a STOP instruction while TMA3 = 1 in active mode, or
by executing a STOP/SBY instruction in subactive mode.
Rev.5.00, Sep.11.2003, page 48 of 161