On Thu, Jun 26, 2003 at 10:42:14PM +0100, Sergio Masci wrote:
> From: Daniel Serpell <daniel@ATMLAB.UTFSM.CL>
> > "lookup_table" should be aligned to a 256 byte boundary, again to avoid
> > 16bit arithmetic. The code is 7cicles each "cbits" macro instead of
> > 12 cicles in my last example, so the total is 81 cycles. That's 47
> > cycles less than the other example, and 256+81=337 words of program
> > memory.
>
> <light hearted tone>
> your 7 cycles do not include the CALL instruction

Yes, I forgot that. So, it adds to 89 cycles.

> Also you can cut the table down by 128 instructions if you post process the
> bottom bit (push it into carry leaving top bit as 0 and cope with it latter), or
> you can cut down the table to 16 bytes and place it in the data eeprom if you
> look at 4 bits at a time.
>
> actually with the 128 element table solution you could collect all the discarded
> bit 0's and add them at the end

Yes, but less elements in the table means more cycle count. At 16 table
entries the no-table approach is faster.

    Daniel.

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