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CHAPTER 24 STANDBY FUNCTION
User’s Manual U12697EJ3V0UM
(b) Releasing the HALT mode
(i) Releasing the HALT mode by NMI input
When the valid edge specified by external interrupt edge enable registers 0 (EGP0, EGN0) is input to
the NMI input, the IDLE mode is released.
When released from the HALT mode, if non-maskable interrupts by the NMI pin input can be
acknowledged, execution branches to the NMI interrupt service program. If interrupts cannot be
acknowledged (when set in the HALT mode by the NMI interrupt service program), execution starts again
from the instruction following the instruction that set the HALT mode. When interrupts can be
acknowledged (by executing the RETI instruction), execution branches to the NMI interrupt service
program.
For details about NMI interrupt acknowledgement, refer to
22.6 Non-Maskable Interrupt Acknowledgment
Operation
.
(ii) Releasing the HALT mode by a maskable interrupt request
An unmasked maskable interrupt request is generated to release the HALT mode.
When the HALT mode is released and the interrupt enable flag (IE) is set to 1, if the interrupt can be
acknowledged, execution branches to interrupt service program. When interrupts cannot be acknowledged
and when the IE flag is cleared to 0, execution restarts from the instruction following the instruction that
set the HALT mode.
For details about interrupt acknowledgement, refer to
22.7 Maskable Interrupt Acknowledgment
Operation
.
(iii) Releasing the HALT mode by RESET input
When RESET input rises from low to high and the reset condition is released, the oscillator starts
oscillating. Oscillation stops for the RESET active period. After the oscillation stabilization time elapses,
normal operation starts.
The difference from the normal reset operation is the data memory saves the contents before setting
the HALT mode.
