Using Powerdown As A Non-Maskable Interrupt - Analog Devices adsp-2100 Manual

9 System Interface
When powerdown is terminated with the RESET pin or if a start-up delay
is selected, a low level on the PWDACK pin only indicates the start of
oscillations on the CLKOUT pin. It will not necessarily indicate the start of
instruction execution.
The state of PWDACK and also the CLKOUT signal is undefined during
the first 100 cycles of initial reset.
9.7.8

Using Powerdown As A Non-Maskable Interrupt

The powerdown interrupt is never masked. It is possible to use this
interrupt for other purposes if desired. The processor will not go into
powerdown until an IDLE instruction is executed. If an RTI is executed
before the IDLE instruction, then the processor returns from the
powerdown interrupt and the powerdown sequence is aborted.
It is possible to place a series of instructions at the powerdown interrupt
vector location 0x002C. This routine should end with an RTI instruction
and not contain an IDLE instruction if the interrupt is to be used for
purposes other than powerdown.
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