PLE8P4                                        PLE DESIGN SPECIFICATION
P5010                                 FRANK LEE/ULRIK MUELLER 10/14/83
8-BIT PRIORITY ENCODER
MMI SANTA CLARA, CALIFORNIA
.ADD I0 I1 I2 I3 I4 I5 I6 I7
.DAT S0 S1 S2 EN


S2 =  I7                                ; I7-I0 = 1XXXXXXX
   +  I6                                ; I7-I0 = X1XXXXXX
   +  I5                                ; I7-I0 = XX1XXXXX
   +  I4                                ; I7-I0 = XXX1XXXX

S1 =  I7                                ; I7-I0 = 1XXXXXXX
   +  I6                                ; I7-I0 = X1XXXXXX
   + /I5*/I4* I3                        ; I7-I0 = XX001XXX
   + /I5*/I4* I2                        ; I7-I0 = XX00X1XX

S0 =  I7                                ; I7-I0 = 1XXXXXXX
   + /I6* I5                            ; I7-I0 = X01XXXXX
   + /I6*/I4* I3                        ; I7-I0 = X0X01XXX
   + /I6*/I4*/I2* I1                    ; I7-I0 = X0X0X01X

EN = /I0*/I1*/I2*/I3*/I4*/I5*/I6*/I7    ; ALL LOWS ENABLE NEXT PRIORITY ENCODER


FUNCTION TABLE

I7 I6 I5 I4 I3 I2 I1 I0 EN S2 S1 S0

;  INPUT   LINES       OUTPUTS
; I I I I I I I I     E   S S S
; 7 6 5 4 3 2 1 0     N   2 1 0       COMMENT
---------------------------------------------------------------
  H X X X X X X X     L   H H H       I7 = HIGH
  L H X X X X X X     L   H H L       I6 = HIGH
  L L H X X X X X     L   H L H       I5 = HIGH
  L L L H X X X X     L   H L L       I4 = HIGH
  L L L L H X X X     L   L H H       I3 = HIGH
  L L L L L H X X     L   L H L       I2 = HIGH
  L L L L L L H X     L   L L H       I1 = HIGH
  L L L L L L L H     L   L L L       I0 = HIGH
  L L L L L L L L     H   L L L       I7-I0 = LOW => CARRY OUT
---------------------------------------------------------------

DESCRIPTION

THIS 8-BIT PRIORITY ENCODER SCANS FOR THE FIRST HIGH INPUT LINE (I7-I0) FROM I7
(WHICH HAS THE HIGHEST PRIORITY) TO I0 (WHICH HAS THE LOWEST PRIORITY).  IT
WILL GENERATE A BINARY ENCODED OUTPUT (S2-S0) WHICH WILL POINT TO THE HIGHEST
PRIORITY INPUT WHICH IS AT A HIGH STATE.

IF NO INPUT LINES ARE HIGH (I7-I0=LOW), THEN THE BINARY ENCODED OUTPUTS WILL BE
ZERO (S2-S0=LOW) AND THE ENABLE OUTPUT WILL BE HIGH (EN=HIGH) INDICATING A
CARRY OUT TO THE NEXT PRIORITY ENCODER.  THE OUTPUT ENABLE WILL BE LOW (EN=LOW)
IF ANY OF THE INPUT LINES ARE HIGH.

THE PLE8P4 ALSO HAS THREE-STATE OUTPUTS WITH TWO ACTIVE-LOW OUTPUT ENABLE
CONTROL PINS (/E1 AND /E2).