HD404654 Datasheet, PDF (29/111 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

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HD404654Series
Stop Mode Cancellation by STOPC: The MCU enters active mode from stop mode by inputting STOPC
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.
Oscillator
Internal
clock
Stop mode
STOPC
or RESET
t_res
STOP instruction execution
t_res ≥ t_RC (stabilization period)
Figure 13 Timing of Stop Mode Cancellation
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