HD404369 Datasheet, PDF (38/117 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404369 Series
Low-power mode
operation cycle
IF = 1 and
No
IM = 0?
Yes
Standby/watch
mode
Stop mode
Hardware NOP
execution
No
IF = 1 and
IM = 0?
Yes
Hardware NOP
execution
No
STOPC = 0?
Yes
RAME = 1
PC ← Next
Iocation
PC ← Next
Iocation
Instruction
execution
Reset MCU
MCU operation
cycle
For IF and IM operation, refer to figure 12.
Figure 19 MCU Operating Sequence (Low-Power Mode Operation)
Note:
When the MCU is in watch mode or subactive mode, if the high level period before the falling edge
of INT₀ is shorter than the interrupt frame, INT₀ is not detected. Also, if the low level period after
the falling edge of INT₀ is shorter than the interrupt frame, INT₀ is not detected. Edge detection is
shown in figure 20. The level of the INT₀ signal is sampled by a sampling clock. When this
sampled value changes to low from high, a falling edge is detected. In figure 21, the level of the
INT₀ signal is sampled by an interrupt frame. In (a) the sampled value is low at point A, and also
low at point B. Therefore, a falling edge is not detected. In (b), the sampled value is high at point
A, and also high at point B. A falling edge is not detected in this case either. When the MCU is in
watch mode or subactive mode, keep the high level and low level period of INT₀ longer than the
interrupt frame
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