dsp56000 Freescale Semiconductor, Inc, dsp56000 Datasheet - Page 74

• Manufacturer Part Number: dsp56000
• Description: 24-bit Digital Signal Processor Family Manual
• Manufacturer: Freescale Semiconductor, Inc

The term bit reverse with respect to reverse-carry arithmetic is descriptive. The lower
boundary that must be used for the bit-reverse address scheme to work is L x (2
previous example shown in Table 4-3, L=3 and k=10. The first address used is the lower
boundary (3072); the calculation of the next address is shown in Figure 4-14. The k LSBs
of the current contents of Rn (3,072) are swapped:
•
•
•
•
•
The result is incremented (3,073), and then the k LSBs are swapped again:
•
•
•
•
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The result is Rn equals 3,584.
4 - 24
Bits 0 and 9 are swapped.
Bits 1 and 8 are swapped.
Bits 2 and 7 are swapped.
Bits 3 and 6 are swapped.
Bits 4 and 5 are swapped.
Bits 0 and 9 are swapped.
Bits 1 and 8 are swapped.
Bits 2 and 7 are swapped.
Bits 3 and 6 are swapped.
Bits 4 and 5 are swapped.
Figure 4-14 Bit-Reverse Address Calculation Example
EACH UPDATE, (Rn)+Nn, IS EQUIVALENT TO:
1. BIT REVERSING:
2. INCREMENT Rn BY 1:
3. BIT REVERSING AGAIN:
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ADDRESSING
Rn=000011 0000000000=3072
Rn=000011 0000000000
Rn=000011 0000000001
000011 0000000001
000011 1000000000=3584
L
1000000000
0000000000
k BITS
+1
MOTOROLA
k
). In the