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CHAPTER 18 STANDBY FUNCTION
(1) Release by non-maskable interrupt
When a non-maskable interrupt is generated, the
m
PD784046 is released from HALT mode irrespective of whether
the interrupt acknowledgment enabled state (EI) or disabled state (DI) is in effect.
When the
m
PD784046 is released from HALT mode, if the non-maskable interrupt that released HALT mode can
be acknowledged, acknowledgment of that non-maskable interrupt is performed and a branch is made to the service
program. If the interrupt cannot be acknowledged, the instruction following the instruction that set the HALT mode
(the MOV STBC, #byte instruction) is executed, and the non-maskable interrupt that released the HALT mode is
acknowledged when acknowledgment becomes possible. Refer to
16.6 Non-Maskable Interrupt Acknowledg-
ment Operation
for details of non-maskable interrupt acknowledgment.
(2) Release by maskable interrupt request
HALT mode release by a maskable interrupt request can only be performed by an interrupt for which the interrupt
mask flag is 0.
When HALT mode is released, if an interrupt can be acknowledged when the interrupt request enable flag (IE) is
set (1), a branch is made to the interrupt service program. If the interrupt cannot be acknowledged and if the IE
flag is cleared (0), execution is resumed from the instruction following the instruction that set the HALT mode. Refer
to
16.7 Maskable Interrupt Acknowledgment Operation
for details of interrupt acknowledgment.
With macro service, HALT mode is released temporarily, service is performed once, then HALT mode is restored.
When macro service has been performed the specified number of times, HALT mode is released. The operation
after release in this case is the same as for release by a maskable interrupt described earlier.
(3) Release by RESET input
The program is executed after branching to the reset vector address, as in a normal reset operation. However,
internal RAM contents retain their value directly before HALT mode was set.