Idma Port During Powerdown (Adsp-2181) - Analog Devices adsp-2100 Manual

While in powerdown, the processor can be reset by writing the HSR
software reset bit. This will produce the same results as asserting the RESET
pin for five cycles (minimum RESET pulse) on the processor. If an external
crystal is used and the clock has been stopped, this reset duration is too
short; therefore software reset cannot be used in this mode. Note that any
HIP activity will increase the power consumption above the 1 mW
specification.
Two mode pins, HMD0 and HMD1, are used to put the processor's HIP into
one of four possible modes. When HMD0 = 1, the HIP data bus is
multiplexed for both address and data. In this case, the HIP data bus inputs
are active during powerdown and any bus activity will result in higher
power dissipation. Also, inputs must be at CMOS levels. If this host mode is
used and there is potential for the bus to be floating, pull-up resistors
should be used on the data lines. If you desire the host to communicate with
other devices on the bus while the DSP processor is in powerdown, HMD0
should be held low to avoid extra power to be dissipated. When the HIP is
put in other modes where data inputs are not active this is not a problem.
Lowest power dissipation is achieved when the HIP pins are not changing
during powerdown and are held at CMOS levels.

9.7.5.4 IDMA Port During Powerdown (ADSP-2181)

The IDMA port can receive data during powerdown, but it can not respond
with an acknowledge (IACK) signal or increment the IDMA internal
address. If you are using a short read or short write and are in the middle of
an IDMA transfer, you can complete a single read or write while the
processor is in powerdown. If you are using the long read or long write
method and are in the middle of an IDMA transfer, your host must be able
to handle a "timeout" condition, as the DSP will not return an acknowledge
to the transfer in process.
Note that IDMA activity while the DSP is in powerdown uses power and
should be avoided to conserve power. For more information on lowest
power use, see "Conditions For Lowest Power Consumption."
System Interface 9
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