HD404459 Datasheet, PDF (36/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

HD404459 Series
STOP/SBY instruction execution
Subactive mode
MCU internal
processing period
(Set LSON = 0, DTON = 1)
Oscillation
stabilization
time
Interrupt strobe
Direct transfer
completion timing
T
t _RC
Active mode
T: Interrupt frame length
t _RC : 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 (i.e., 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: See figures 20 to 22 for the MCU operation sequences. 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.
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