Syntax:

• LUTINVSQRT Rd3 BS Rs1

Description:

Returns in register Rd3 the leading term of iterative algorithm to compute 1/(square root of x), where x is the content of Rs1. Instruction is performed according to BS (bank select) and is stack conditioned.

Microcode Pattern:

Takes 4 cycles to execute.
    Example: LUTINVSQRT 0xA3 3 0xA1

	  
	MPC  BS3 C3 P3 P1
	-----------------
	ISQ   0  0  00 A1
	 -    0  0  00 00
	 -    0  0  00 00
	 -    3  0  A3 00

	  

Exceptions :

Exceptional cases of LUTINVSQRT are limited to operands that are either zero, infinity or negative as seen in table below (in all these cases, mantissa is set to zero):

SRs1(hex)	ERs1(hex)	ERd3(hex)	Exceptions
x	0x7FF	0x7FF	BADOP
x	0x000	0x7FE	OVF
1	x	0x7FF	OVF

Example :

LUTINVSQRT 0x21 1 0x20 
  !! Perform 1/(square root of x),
  !! where x is the content of low 
  !! bank of register 0x21 and puts 
  !! the value in low bank of 0x21