HD404374FT datasheet(48/161 Pages) RENESAS

48 / 161 page

HD404374/HD404384/HD404389/HD404082/HD404084 Series

Rev.5.00, Sep.11.2003, page 48 of 161

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 OSC

1 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

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

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.

Stop mode

Oscillator

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 OSC

1 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.

HD404374FT Datasheet(PDF) 48 Page - Renesas Technology Corp