HD404618 Datasheet, PDF (31/91 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

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Oscillator
Internal clock
Stop mode
HD404618 Series
RESET
t _res
STOP instruction execution
t _res> t _RC (stabilization time)
Figure 12 Timing of Stop Mode Cancellation
Watch Mode: The MCU enters watch mode if the STOP instruction is executed in active mode when
TMA3 = 1, or if the STOP or SBY instruc-tion is executed in subactive mode.
Watch mode is terminated by a RESET input or a timer-A/INT₀ interrupt request. For details of RESET
input, refer to the Stop Mode section. When terminated by a timer-A/INT₀ 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 13.
Operation during mode transition is the same as that at standby mode cancellation (figure 12).
Active mode
Watch mode
Oscillation
stabilization period
Active mode
Interrupt strobe
INT₀
Interrupt request
generation
(During the transition
from watch mode to
active mode only)
T
T
t _RC
Tx
T = 2 × t_RC: Interrupt frame length
t_RC: Oscillation stabilization period
Figure 13 Interrupt Frame
Subactive Mode: The CPU operates with a clock generated by the X1 and X2 oscillation circuits.
Functions that can operate in subactive mode are listed in table 16. When the STOP or SBY instruction is
executed in subactive mode, the MCU enters either watch or active mode, depending on the statuses of
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