
HD404449 Series
34
Subactive mode
Interrupt strobe
Direct transfer
completion timing
MCU internal
processing period
Oscillation
stabilization
time
Active mode
T
t
RC
T:
t :
STOP/SBY instruction execution
(Set LSON = 0, DTON = 1)
Interrupt frame length
Oscillation stabilization period
Figure 19 Direct Transition Timing
Stop Mode Cancellation by
STOPC
: The MCU enters active mode from stop mode by a
STOPC
input
as well as by RESET. In either case, the MCU starts instruction execution from the starting address
(address 0) of the program. However, the value of the RAM enable flag (RAME: $021, bit 3) differs
between cancellation by
STOPC
and by RESET. When stop mode is cancelled by RESET, RAME = 0;
when cancelled by
STOPC
, RAME = 1. RESET can cancel all modes, but
STOPC
is valid only in stop
mode;
STOPC
input is ignored in other modes. Therefore, when the program requires to confirm that stop
mode has been cancelled by
STOPC
(for example, when the RAM contents before entering stop mode are
used after transition to active mode), execute the TEST instruction on the RAM enable flag (RAME) at the
beginning of the program.
MCU Operation Sequence:
The MCU operates in the sequences shown in figures 20 to 22. It is reset by
an asynchronous RESET input, regardless of its status.
The low-power mode operation sequence is shown in figure 22. 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.