Re: [oc] "1/x" function

[John Kent <jekent@optushome.com.au>]

Hi,

I'll buy into this thread, simply because I need to implement a 
Fractional Divide and Integer
divider for a 68HC11 I'm working on.

A fractional divide should be relatively easy, given that 1/x is a 
fractional if X is an integer

Given a fractional 32 bit numerator, and a 16 bit denominator, isn't it 
simply a matter
of doing a multiply in reverse.
ie.
If X is an integer you will probably have to have some leading zeros on 
the numerator..

compare the left justified denominator with the numerator.
if the denominator is less than the numerator, subtact the denominator 
to form a new numerator
and set the least significant bit in the integer result
right shift the denominator one bit, left shift the integer result one 
bit and repeat the process
16 times for a 32 bit numerator and a 16 bit denominator. The remainder 
will be in the numerator.

The design should be easily pipe lined.

I'm not sure if this is what people were getting at when they said to do 
it with a multiply.
My appologies if I am stating the obvious. I suspect I might have missed 
the point.

If someone can confirm I'm on the right track, I might give the 68HC11 
IDIV and FDIV another try.

John.

Rudolf Usselmann wrote:

>Anybody have an efficient algorithm for a "1/x" function for
>hardware implementations ? Or any pointer to white papers, etc ?
>I need something that is fast and small, and can be pipelined.
>
>Any pointers appreciated !
>
>Thanks,
>  
>

-- 
http://members.optushome.com.au/jekent



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