Analog Devices ADSP-BF53x Blackfin, Reference

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Addressing With the AAU
5-12 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
For example:
R2 = W [ P4++P5 ] (Z) ;
loads a 16-bit word into the low half of the destination register
R2
and
zero-extends it to 32 bits. The value of the pointer
P4
is incremented by
the value of the pointer
P5
.
For example:
R2 = [ I2++M1 ]
;
loads a 32-bit word into the destination register
R2
. The value in the Index
register,
I2
, is updated by the value in the Modify register,
M1
.
Addressing Circular Buffers
The DAGs support addressing circular buffers. Circular buffers are a range
of addresses containing data that the DAG steps through repeatedly,
wrapping around to repeat stepping through the same range of addresses
in a circular pattern.
The DAGs use four types of data address registers for addressing circular
buffers. For circular buffering, the registers operate this way:
• The Index (I) register contains the value that the DAG outputs on
the address bus.
• The Modify (M) register contains the post-modify amount (posi-
tive or negative) that the DAG adds to the I-register at the end of
each memory access.
Any M-register can be used with any I-register. The modify value
can also be an immediate value instead of an M-register. The size of
the modify value must be less than or equal to the length (L-regis-
ter) of the circular buffer.