Grant Griffin wrote:

> A friend asked me today how to transpose an array of bits on the 
> Blackfin.  Bascially, the requirement is to turn columns of bits into 
> rows, as follows:
> 
>     Word 1: a1 b1 c1 d1 ...
>     Word 2: a2 b2 c2 d2 ...
>     ...
> 
> becomes:
> 
>     Word 1: a1 a2 a3 a4 ...
>     Word 2: b1 b2 b3 b4 ...
>     ...
> 
> Each input word contains 12 useful bits within a 16-bit word, with 4 
> bits unused.  The output words can be 8, 16, or 32 bits - whatever is 
> most efficient.
> 
> The straight-forward method of doing this might be too slow for the 
> application.  Does anybody know a fast way to do this, possibly using 
> special Blackfin assembly constructs?

The BITMUX instruction processes 2 bits and 2 words at a time.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

A friend asked me today how to transpose an array of bits on the 
Blackfin.  Bascially, the requirement is to turn columns of bits into 
rows, as follows:

	Word 1: a1 b1 c1 d1 ...
	Word 2: a2 b2 c2 d2 ...
	...

becomes:

	Word 1: a1 a2 a3 a4 ...
	Word 2: b1 b2 b3 b4 ...
	...

Each input word contains 12 useful bits within a 16-bit word, with 4 
bits unused.  The output words can be 8, 16, or 32 bits - whatever is 
most efficient.

The straight-forward method of doing this might be too slow for the 
application.  Does anybody know a fast way to do this, possibly using 
special Blackfin assembly constructs?

thanks,

Grant

p.s.  I promise this isn't a homework problem.  Honest it isn't.

-- 
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Grant R. Griffin
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