SDKZSPF LSI, SDKZSPF Datasheet - Page 342

• Manufacturer Part Number: SDKZSPF
• Manufacturer: LSI

Specifications of SDKZSPF

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E.8
E.8.1
E-10
API Specification for Inverse Square Root Library
Function on G2
Inverse Square Root
Synopsis
Xout lib_invsqrt( Xi )
Input
Short Xi
(1.99999)
Return
short Xout Q14 number in the range 0x1000 (0.25) < Xi < 0x7fff
(1.99999)
Description
Calculate the inverse square root of an input Xi.
Xout = 1/sqrt( Xi )
Technique employs a look up table to obtain a first approximation to
Xout.
The approximation Xout is then used by following recursive algorithm to
calculate a more precise value for Xout.
Xout = (3/2)*Xout - (Xi * Xout^3)/2
Three iterations of the above algorithm are performed
Signal Processing Library
Copyright © 1999-2003 by LSI Logic Corporation. All rights reserved.
Q14 number in the range 0x1000 (0.25) < Xi < 0x7fff