Addressing With Bit-Reversed Addresses; Modifying Dag And Pointer Registers - Analog Devices ADSP-BF53x Blackfin Reference

In equation form, these post-modify and wraparound operations work as
follows, shown for "I+M" operations.
• If M is positive:
I = I
new
if I + M < buffer base + length (end of buffer)
old
I = I
new
+ M ≥ buffer base + length (end of buffer)
if I
old
• If M is negative:
I = I
new
+ M ≥ buffer base (start of buffer)
if I
old
I = I
new
if I + M < buffer base (start of buffer)
old

Addressing With Bit-reversed Addresses

To obtain results in sequential order, programs need bit-reversed carry
addressing for some algorithms, particularly Fast Fourier Transform
(FFT) calculations. To satisfy the requirements of these algorithms, the
DAG's bit-reversed addressing feature permits repeatedly subdividing data
sequences and storing this data in bit-reversed order. For detailed infor-
mation about bit-reversed addressing, see
page 15-37.

Modifying DAG and Pointer Registers

The DAGs support operations that modify an address value in an Index
register without outputting an address. The operation, address-modify, is
useful for maintaining pointers.
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
+ M
old
+ M – L
old
+ M
old
+ M + L
old
Address Arithmetic Unit
"Modify – Increment" on
5-15