HD404449 Datasheet, PDF (30/123 Pages) Hitachi Semiconductor – HD404449 SERIES

HD404449 Series
Standby Mode: In standby mode, the oscillators continue to operate, but the clocks related to instruction
execution stop. Therefore, the CPU operation stops, but all RAM and register contents are retained, and the
D or R port status, when set to output, is maintained. Peripheral functions such as interrupts, timers, and
serial interface continue to operate. The power dissipation in this mode is lower than in active mode
because the CPU stops.
The MCU enters standby mode when the SBY instruction is executed in active mode.
Standby mode is terminated by a RESET input or an interrupt request. If it is terminated by RESET input,
the MCU is reset as well. After an interrupt request, the MCU enters active mode and executes the next
instruction after the SBY instruction. If the interrupt enable flag is 1, the interrupt is then processed; if it is
0, the interrupt request is left pending and normal instruction execution continues. A flowchart of
operation in standby mode is shown in figure 15.
Stop
Standby
Oscillator: Stop
Suboscillator: Active/Stop
Peripheral clocks: Stop
All other clocks: Stop
Oscillator: Active
Peripheral clocks: Active
All other clocks: Stop
Watch
Oscillator: Stop
Suboscillator: Active
Peripheral clocks: Stop
All other clocks: Stop
No
RESET = 1?
Yes
No
STOPC = 0?
Yes
RAME = 1
No
RESET = 1?
Yes _{IF0 • IM0 = 1? No}
Yes
No
IF1 • IM1 = 1?
RAME = 0
Yes
(SBY
only)
IFTA • IMTA ^No
= 1?
Yes
IFTB •
IMTB + IF2 •
No
IM2 = 1?
Yes
IFTC •
IMTC + IF3 •
No
IM3 = 1?
(SBY
only)
Yes
IFTD •
IMTD + IFAD •
No
IMAD = 1?
Yes
IFS1•
IMS1 + IFS2 •
No
IMS2 = 1?
(SBY
only)
(SBY
only)
(SBY _Yes
only)
Restart
processor clocks
Restart
processor clocks
Execute
next instruction
Reset MCU
No
Execute
next instruction
IF = 1,
IM = 0, and
IE = 1?
Yes
Accept interrupt
Figure 15 MCU Operation Flowchart
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