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NEC PD754244 Manuel D’Utilisation

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CHAPTER 8   STANDBY FUNCTION
218
User’s Manual  U10676EJ3V0UM
8.2  Releasing Standby Mode
Both the STOP and HALT modes can be released when an interrupt request signal occurs that is enabled by the
corresponding interrupt enable flag, or when the RESET signal is asserted.  Furthermore, STOP mode can be released
without altering the interrupt enable flag, when the KRREN pin is high, by using a falling edge input (key return reset)
at the KRn pin.
Figure 8-1 illustrates how each mode is released.
Figure 8-1.  Releasing Standby Mode (1/2)
(a) Releasing STOP mode by RESET signal, or by key return reset
Clock
STOP 
instruction
Operation 
mode
STOP mode
Oscillates
Stops
HALT mode 
Oscillates
Wait
Note 1
Operation 
mode
RESET
signal, KRn 
(b) Releasing STOP mode by interrupt (except for releasing by key return reset)
Standby release
signal
Clock
STOP 
instruction
Operation 
mode
STOP mode
Stops
HALT mode 
Oscillates
Wait
Note 2
Operation 
mode
Oscillates
Notes
1.
µPD754244: The following two times can be selected by mask option.
2
17
/f
X
 (21.8 ms at 6.0 MHz, 31.3 ms at 4.19 MHz)
2
15
/f
X
 (5.46 ms at 6.0 MHz, 7.81 ms at 4.19 MHz)
µPD754144: The wait time is fixed to 56/f
CC
 (56 
µs at 1.0 MHz)
2.
µPD754244: The time is set by BTM.
µPD754144: This time is fixed to 2
9
/f
CC
 (512 
µs at 1.0 MHz).
Remark
The broken lines indicate acknowledgment of the interrupt request that releases the standby mode.