PLE12P8                                              PLE DESIGN SPECIFICATON
P5020                                                     FRANK LEE 10/14/83
ARITHMETIC LOGIC UNIT
MMI SNATA CLARA, CALIFORNIA
.ADD A3 A2 A1 A0 B3 B2 B1 B0 CIN I2 I1 I0
.DAT C3 C2 C1 C0 Z V C

;************************************************
;*  THIS DESIGN IS NOT YET SUPPORTED BY PLEASM  *
;************************************************


C,C3,C2,C1,C0 = /S2*/S1* S0*/A3,/A2,/A1,/A0         ;B - A - 1 + CIN
                    .+. B3, B2, B1, B0.+. CIN
              + /S2* S1*/S0* A3, A2, A1, A0         ;A - B - 1 + CIN
                    .+./B3,/B2,/B1,/B0.+. CIN
              + /S2* S1* S0* A3, A2, A1, A0         ;A + B + CIN
                    .+. B3, B2, B1, B0.+. CIN
              +  S2*/S1*/S0*/A3,/A2,/A1,/A0         ;A XOR B
                    :*: B3, B2, B1, B0
              +  S2*/S1* S0* A3, A2, A1, A0         ;A + B
                    +  S2*/S1* S0* B3, B2, B1, B0
              +  S2* S1*/S0* A3, A2, A1, A0         ;A * B
                    * B3, B2, B1, B0
              +  S2* S1* S0                         ;PRESET

V             =  C:+: C3                            ;OVERFLOW

Z             = /C3*/C2*/C1*/C0                     ;ZERO


DESCRIPTION

THIS ALU CAN PERFORM 8 FUNCTIONS ON TWO 4-BIT OPERANDS A (A3-A0) AND
B (B3-B0) WITH CARRYIN (CIN) AND GIVES A 4-BIT RESULT C (C3-C0) WITH
CARRYOUT (C).  IT WILL ALSO GIVE STATUS AS OVERFLOW (V) AND ZERO (Z).

THE FUNCTION IS DETERMINED BY A 3-BIT FUNCTION SELECT CODE (S2-S0):

                       MODE   S2 S1 S0  FUNCTION
                      ----------------------------------
                         0     0  0  0  CLEAR
                         1     0  0  1  B - A - 1 + CIN
                         2     0  1  0  A - B - 1 + CIN
                         3     0  1  1  A + B + CIN
                         4     1  0  0  A XOR B
                         5     1  0  1  A + B
                         6     1  1  0  A * B
                         7     1  1  1  PRESET
                      ----------------------------------