Syntax:

• LUTINV Rd3 BS Rs1

Description:

Returns in register Rd3 the leading term of iterative algorithm to get 1/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: LUTINV 0xA3 3 0xA1

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

	  

Exceptions :

The following exceptional cases are handled as specified in table below (in all these cases, mantissa is set to zero):

ERs1(hex)	mRs1(42:42)	ERd3(hex)	Exceptions
0x7FF	x	0x7FF	BADOP
0x7FE	x	0x000	OUT_DEN
0x7FD	x	0x000	OUT_DEN
0x000	x	0x7FF	OVF
0x3FF	0*	0x3FF	-

^*- is a special case such that if the argument is close to 1.0 then 1.0 is returned.

Example :

LUTINV 0x21 1 0x20 
  !! Perform 1/x, where x is the 
  !! content of low bank of 0x20
  !! and puts the value in low
  !! bank of register 0x21