HD404318 Datasheet, PDF (22/68 Pages) Hitachi Semiconductor – 4-bit HMCS400-series microcomputer

HD404318 Series
MCU Operation Sequence: The MCU operates in the sequence shown in figure 13 and figure 14.
The low-power mode operation sequence is shown in figure 14. With the IE flag cleared and an interrupt
flag set together with its interrupt mask cleared, if a STOP/SBY instruction is executed, the instruction is
cancelled (regarded as an NOP) and the following instruction is executed. Before executing a STOP/SBY
instruction, make sure all interrupt flags are cleared or all interrupts are masked.
Power ON
RESET = 0? ^No
Yes
RAME = 0
Reset MCU
Reset input
MCU operation cycle
IF = 1?
No
Yes
No
IRnAstMruEct=io1n
execution
IM = 0
IE = 1
Yes
Low-power mode
operation cycle
(figure 15)
SBY/STOP
instruction
No
PC ← (PC)+1
IE ← 0
Stack ← (PC),
(CA), (ST)
PC ← vector
address
Figure 13 MCU Operating Sequence (Power ON)
20