PAL16R4                                              PAL DESIGN SPECIFICATION
P7096                                                   WILLY VOLDAN 09/09/82
SHAFT ENCODER No. 1
MMI GMBH MUNICH
CLK PHI0 PHI90 X4 NC NC NC NC /SET GND
/OC DOWN  NC   S4 S3 S2 S1 NC  UP  VCC


/S1 :=  /PHI0                                                 ;CHECK FOR PHI0
     +   SET                                                  ;INITIALIZE S1=L

/S2 :=  /S1                                                   ;CHECK FOR S1
     +   SET                                                  ;INITIALIZE S2=L

/S3 :=  /PHI90                                                ;CHECK FOR PHI90
     +   SET                                                  ;INITIALIZE S3=L

/S4 :=  /S3                                                   ;CHECK FOR S3
     +   SET                                                  ;INITIALIZE S4=L

IF (VCC) /DOWN =  S1* S2* S3*/S4* PHI0* PHI90                 ;PHI0 LEADS PHI90
               + /S1*/S2*/S3* S4*/PHI0*/PHI90                 ;PHI0 LEADS PHI90
               +  S1*/S2*/S3*/S4* PHI0*/PHI90                 ;PHI0 LEADS PHI90
               + /S1* S2* S3* S4*/PHI0* PHI90                 ;PHI0 LEADS PHI90

IF (VCC) /UP   = /S1*/S2* S3*/S4*/PHI0* PHI90                 ;PHI90 LEADS PHI0
               +  S1* S2*/S3* S4* PHI0*/PHI90                 ;PHI90 LEADS PHI0
               +  S1*/S2* S3* S4* PHI0* PHI90                 ;PHI90 LEADS PHI0
               + /S1* S2*/S3*/S4*/PHI0*/PHI90                 ;PHI90 LEADS PHI0


FUNCTION TABLE

CLK /OC /SET PHI0 PHI90 S4 S3 S2 S1 UP DOWN

;---CONTROLS---      --INPUTS--      SSSS      OUTPUTS
;CLK  /OC  /SET      PHI0 PHI90      4321      UP DOWN      COMMENTS
-------------------------------------------------------------------------------
  C    L     L        X     X        LLLL      H   H        CLEAR REGISTERS
  C    L     H        L     L        LLLL      H   H
  C    L     H        L     L        LLLL      H   H
  C    L     H        L     H        LHLL      L   H        COUNT UP
  C    L     H        L     H        HHLL      H   H
  C    L     H        H     H        HHLH      L   H        COUNT UP
  C    L     H        H     H        HHHH      H   H
  C    L     H        H     L        HLHH      L   H        COUNT UP
  C    L     H        H     L        LLHH      H   H
  C    L     H        L     L        LLHL      L   H        COUNT UP
  C    L     H        L     L        LLLL      H   H
  C    L     H        L     H        LHLL      L   H        COUNT UP
  C    L     H        L     H        HHLL      H   H
  C    L     H        H     H        HHLH      L   H        COUNT UP
  C    L     H        H     H        HHHH      H   H
  C    L     H        H     L        HLHH      L   H        COUNT UP
  C    L     H        H     L        LLHH      H   H
  C    L     H        L     L        LLHL      L   H        COUNT UP
  C    L     H        L     L        LLLL      H   H
  C    L     H        L     H        LHLL      L   H        COUNT UP
  C    L     H        L     H        HHLL      H   H
  C    L     H        H     H        HHLH      L   H        COUNT UP
  C    L     H        H     H        HHHH      H   H
  C    L     H        H     L        HLHH      L   H        COUNT UP
  C    L     H        H     L        LLHH      H   H
  C    L     H        L     L        LLHL      L   H        COUNT UP
  C    L     H        L     L        LLLL      H   H
  C    L     L        X     X        LLLL      H   H        CLEAR REGISTERS
  C    L     H        L     L        LLLL      H   H
  C    L     H        L     L        LLLL      H   H
  C    L     H        H     L        LLLH      H   L        COUNT DOWN
  C    L     H        H     L        LLHH      H   H
  C    L     H        H     H        LHHH      H   L        COUNT DOWN
  C    L     H        H     H        HHHH      H   H
  C    L     H        L     H        HHHL      H   L        COUNT DOWN
  C    L     H        L     H        HHLL      H   H
  C    L     H        L     L        HLLL      H   L        COUNT DOWN
  C    L     H        L     L        LLLL      H   H
  C    L     H        H     L        LLLH      H   L        COUNT DOWN
  C    L     H        H     L        LLHH      H   H
  C    L     H        H     H        LHHH      H   L        COUNT DOWN
  C    L     H        H     H        HHHH      H   H
  C    L     H        L     H        HHHL      H   L        COUNT DOWN
  C    L     H        L     H        HHLL      H   H
  C    L     H        L     L        HLLL      H   L        COUNT DOWN
  C    L     H        L     L        LLLL      H   H
  C    L     H        H     L        LLLH      H   L        COUNT DOWN
  C    L     H        H     L        LLHH      H   H
  C    L     H        H     H        LHHH      H   L        COUNT DOWN
  C    L     H        H     H        HHHH      H   H
  C    L     H        L     H        HHHL      H   L        COUNT DOWN
  C    L     H        L     H        HHLL      H   H
  C    L     H        L     L        HLLL      H   L        COUNT DOWN
  C    L     H        L     L        LLLL      H   H
  X    H     X        X     X        ZZZZ      X   X        TEST HI-Z
-------------------------------------------------------------------------------


DESCRIPTION:

THIS PAL16R4 IMPLEMENTS A TWO CHANNEL SHAFT ENCODER OF THE TYPE USED IN SPEED
CONTROLLERS AND OPTICAL DEVICES.

BOTH THE "UP" AND "DOWN" OUTPUTS OF THE PAL ARE NORMALLY HIGH.

WHEN THE SIGNAL AT THE "PHI0" INPUT LEADS THE SIGNAL AT THE "PHI90" INPUT, THE
"DOWN" OUTPUT ALTERNATES BETWEEN HIGH AND LOW LEVELS AT HALF THE "CLK"
FREQUENCY RATE.  ALSO, WHEN THE SIGNAL AT THE "PHI0" INPUT LAGS THE SIGNAL AT
THE "PHI90" INPUT, THE "UP" OUTPUT ALTERNATES BETWEEN HIGH AND LOW LEVELS AT
HALF THE "CLK" FREQUENCY RATE.

THE SHAFT ENCODER FEATURES THE CONFIGURATION AND OUTPUT POLARITY TO DRIVE AN
74S193 TYPE UP/DOWN COUNTER.

THIS DESIGN WITH GLITCHFREE OUTPUTS WILL BE EXTREMELY USEFUL IN ELECTRICALLY
NOISY ENVIRONMENTS.  THE PINNING IS GIVEN AS A FIRST PROPOSAL AND CAN BE
CHANGED ACCORDING TO THE PC-BOARD LAYOUT.