Re: - Need fast divide by 14 constant routine? ( Random access 8-bit data in PIC16F flash )

by Spehro Pefhany :: Rate this Message:

Quoting Ed Sutton <esutton@...>:

> Are there other ways to implement a divide by a 14 constant other than
> cycle-chewing subtraction loops?
>
> I want to use the PIC16F flash consisting of 14-bit words to store 8-bit
> data. I can implement the multiply-by-8 as a shift. The crux of the
> problem is basically the divide by a constant of 14.
>
> Pseudo Code ( actual code will likely be assembly )
>
> wordOffset = 8*byteOffset / 14; // The integer result
> wordBitOffset = 8*byteOffset % 14; // The remainder result

Since you need both the quotient and the remainder, and cannot tolerate
any error in either, I think a conventional shift-and-subtract
division routine
will work pretty well and will generate both numbers at once. Did you
check the PICLIST code library?

Best regards,
Spehro Pefhany
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