PLE5P8                                              PLE DESIGN SPECIFICATION
P5023                                                PETER ZECHERLE 03/06/84
ARC TANGENT LOOK-UP TABLE
MMI GMBH MUNICH
.ADD A0 A1 A2 A3 A4
.DAT F0 F1 F2 F3 F4 F5 F6 F7


F0 =     A1*     /A3*/A4      ; COMPUTE DIGIT FOR 2EXP-7 (0.00078125) (LSB)
   +          A2*/A3
   +  A0*/A1*     A3*/A4
   + /A0* A1*        /A4
   + /A0*/A1*    /A3* A4
   +  A0*     A2
   +      A1* A2

F1 =     /A1*     A3*/A4      ; COMPUTE DIGIT FOR 2EXP-6 (0.015625)
   +  A0*        /A3* A4
   +      A1*    /A3* A4
   +          A2*/A3* A4
   +  A0* A1*    /A3
   +  A0*     A2*/A3
   + /A0* A1* A2*    /A4
   +  A0*    /A2* A3*/A4

F2 =  A0*        /A3*/A4      ; COMPUTE DIGIT FOR 2EXP-5 (0.03125)
   +      A1*/A2*    /A4
   +              A3* A4
   + /A0*     A2* A3*/A4
   +     /A1* A2* A3*/A4 

F3 =      A1*/A2*    /A4      ; COMPUTE DIGIT FOR 2EXP-4 (0.0625)
   +     /A1* A2*    /A4
   + /A0*         A3*/A4
   +     /A1*     A3*/A4

F4 =     /A1*     A3*/A4      ; COMPUTE DIGIT FOR 2EXP-3 (0.125)
   +  A0* A1*/A2*    /A4
   +      A1* A2*/A3*/A4
   + /A0*         A3*/A4

F5 =  A0*/A1*        /A4      ; COMPUTE DIGIT FOR 2EXP-2 (0.25)
   +          A2*/A3*/A4
   +         /A2* A3*/A4
   + /A0*         A3*/A4

F6 =  A0*/A1*/A2*/A3          ; COMPUTE DIGIT FOR 2EXP-1 (0.5)
   +  A0* A1* A2* A3
   +                  A4

F7 =      A1                  ; COMPUTE DIGIT FOR 2EXP0 (1) (MSB)
   +          A2
   +              A3
   +                  A4


FUNCTION TABLE

;----ANGLE----    --------F = ARCTAN(A)--------
;   INTEGER       INTEGER       FRACTIONS                   ---F = ARCTAN(A)---
A4 A3 A2 A1 A0       F7    F6 F5 F4 F3 F2 F1 F0    ;ANGLE   LOOK-UP  CALCULATED
-------------------------------------------------------------------------------
L  L  L  L  L        L     L  L  L  L  L  L  L        0      0.0000    0.0000
L  L  L  L  H        L     H  H  L  L  H  L  L        1      0.7813    0.7854
L  L  L  H  L        H     L  L  L  H  H  L  H        2      1.1016    1.1071
L  L  H  L  L        H     L  H  L  H  L  L  H        4      1.3203    1.3258
L  L  H  L  H        H     L  H  L  H  H  H  H        5      1.3672    1.3734
L  H  L  L  L        H     L  H  H  H  L  H  L        8      1.4531    1.4464
H  L  L  L  L        H     H  L  L  L  L  L  H       16      1.5078    1.5084
H  H  H  H  H        H     H  L  L  L  H  L  H       31      1.5391    1.5385
-------------------------------------------------------------------------------


DESCRIPTION

THIS APPLICATION ILLUSTRATES THE CALCULATION OF THE ARC TANGENT FUNCTION USING
A PLE5P8 AS A LOOK-UP TABLE.  OTHER TRIGONOMETRIC FUNCTIONS (SUCH AS SINE,
COSINE, COTANGENT, SECANT, COSECANT AND THEIR ARC INVERSE EQUIVALENT FUNCTIONS)
OR HYPERBOLIC FUNCTIONS CAN ALSO BE CONSTRUCTED USING PLES AS LOOK-UP TABLES.

F = ARCTAN(A)     WHERE F = ARC TANGENT OF A
                        A = ANGLE IN RADIANS

EXAMPLE:  FOR A = 5, F = ARCTAN(5) = 1.3672

A PLE WITH MORE INPUTS, SUCH AS THE PLE11P8, SHOULD BE USED TO CONSTRUCT A
LOOK-UP TABLE WHEN ADDITIONAL ACCURACY IS REQUIRED.
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