HD404459 Datasheet, PDF (33/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers


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HD404459Series
Stop Mode: In stop mode, all MCU operations stop and RAM data is retained. Therefore, the power
dissipation in this mode is the least of all modes. The OSC₁ and OSC₂ oscillator stops. Operation of the X1
and X2 oscillator can be selected by setting bit 3 of the system clock select register (SSR1: $029; operating:
SSR13 = 0, stop: SSR13 = 1) (figure 24). The MCU enters stop mode if the STOP instruction is executed in
active mode when bit 3 of timer mode register A (TMA: $008) is set to 0 (TMA3 = 0) (figure 40).
Stop mode is terminated by RESET input or STOPC input (figure 16). RESET or STOPC must be applied
for at least one t_RC to stabilize oscillation (refer to the AC Characteristics section). When the MCU restarts
after stop mode is cancelled, all RAM contents before entering stop mode are retained, but the accuracy of
the contents of the accumulator, B register, W register, X/SPX register, Y/SPY register, carry flag, and
serial data register cannot be guaranteed.
Oscillator
Internal
clock
Stop mode
RESET
STOPC
STOP instruction execution
t_res
t_res ≥ t_RC (stabilization period)
Figure 16 Timing of Stop Mode Cancellation
Watch Mode: In watch mode, the clock function (timer A) using the X1 and X2 oscillator operate but
other function operations stop. Therefore, the power dissipation in this mode is the second least to stop
mode, and is also convenient when only clock display is used. In this mode, the OSC₁ and OSC₂ oscillator
stops, but the X1 and X2 oscillator operates. The MCU enters watch mode if the STOP instruction is
executed in active mode when TMA3 = 1, or if the STOP or SBY instruction is executed in subactive
mode.
Watch mode is terminated by a RESET input, timer A interrupt request, INT₀ interrupt request, or wakeup
interrupt request. For details of RESET input, refer to the Stop Mode section. When terminated by a timer
A interrupt request, an INT₀ nterrupt request, or wakeup interrupt request, the MCU enters active mode if
LSON is 0 or subactive mode if LSON is 1. After an interrupt request is generated, the time required to
enter active mode is t_RC for a timer A interrupt, and T_X (where T + t_RC < T_X < 2T + t_RC) for an INT₀
interrupt, as shown in figure 17.
Operation during mode transition is the same as that at standby mode cancellation (figure 15).
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