PAL20X10                                           PAL DESIGN SPECIFICATION
P7052                                              BIRKNER/UDI     07/14/81
LINES/SCROL GENERATOR
MMI SUNNYVALE, CALIFORNIA
 CK /SWAP    SCAN0   SCAN1  /INIT   /SCAN3   /H255   NC     /WRITE  /LINE4
/INCSCR GND /OC     /SCROL0 /LINES0 /SCROL1 /LINES1 /SCROL2 /LINES2 /SCROL3
/LINES3 /INITS /OE  VCC


LINES0  :=  /SWAP*/INITS*LINES0                    ;HOLD
         +   SWAP*/INITS*SCROL0                    ;SWAP WITH SCROL
        :+: /SWAP*/INITS*H255*/LINE4               ;INC (12 DOT LINES)
         * SCAN3*SCAN1*SCAN0
         +  /SWAP*/INITS*INCSCR                    ;INC (LF)

SCROL0  :=  /SWAP*/INITS*SCROL0                    ;HOLD
         +   SWAP*/INITS*LINES0                    ;SWAP WITH LINES
        :+: /SWAP*/INITS*INCSCR                    ;INC (LF OR CHAR = 47)
         +         INITS                           ;INITIALIZE

LINES1  :=  /SWAP*/INITS*LINES1                    ;HOLD
         +   SWAP*/INITS*SCROL1                    ;SWAP WITH SCROL
        :+: /SWAP*/INITS*H255*/LINE4               ;INC (12 DOT LINES)
                 * SCAN3*SCAN1*SCAN0*LINES0
         +  /SWAP*/INITS*INCSCR*LINES0             ;INC (LF)

SCROL1  :=  /SWAP*/INITS*SCROL1                    ;HOLD
         +   SWAP*/INITS*LINES1                    ;SWAP WITH LINES
        :+: /SWAP*/INITS*INCSCR*SCROL0             ;INC (LF OR CHAR = 47)
         +         INITS                           ;INITIALIZE

LINES2  :=  /SWAP*/INITS*LINES2                    ;HOLD
         +   SWAP*/INITS*SCROL2                    ;SWAP WITH SCROL
        :+: /SWAP*/INITS*H255*/LINE4               ;INC (12 DOT LINES)
                 * SCAN3*SCAN1*SCAN0
                 *LINES1*LINES0
         +  /SWAP*/INITS*INCSCR                    ;INC (LF)
                 *LINES1*LINES0

SCROL2  :=  /SWAP*/INITS*SCROL2                    ;HOLD
         +   SWAP*/INITS*LINES2                    ;SWAP WITH LINES
        :+: /SWAP*/INITS*INCSCR*SCROL0*SCROL1      ;INC (LF OR CHAR = 47)
         +         INITS                           ;INITIALIZE

LINES3  :=  /SWAP*/INITS*LINES3                    ;HOLD
         +   SWAP*/INITS*SCROL3                    ;SWAP WITH SCROL
        :+: /SWAP*/INITS*H255*/LINE4               ;INC (12 DOT LINES)
                 * SCAN3*SCAN1*SCAN0
                 *LINES2*LINES1*LINES0
         +  /SWAP*/INITS*INCSCR                    ;INC (LF)
                 *LINES2*LINES1*LINES0

SCROL3  :=  /SWAP*/INITS*SCROL3                    ;HOLD
         +   SWAP*/INITS*LINES3                    ;SWAP WITH LINES
        :+: /SWAP*/INITS*INCSCR                    ;INC (LF OR CHAR = 47)
                 *SCROL2*SCROL1*SCROL0
         +         INITS                           ;INITIALIZE

INITS   :=  INIT*H255                              ;INITIALIZATION SIGNAL

OE      := /WRITE                                  ;ENABLE THREE STATE OF RAM


FUNCTION TABLE

CK    SWAP   SCAN3  SCAN1  SCAN0  INIT   H255   WRITE LINE4  INCSCR /OC
SCROL3 SCROL2 SCROL1 SCROL0 LINES3 LINES2 LINES1 LINES0  INITS   OE

;                         I
;                   W  L  N                   I
;    S        I  H  R  I  C                   N
;    W        N  2  I  N  S  /                I
; C  A  SCAN  I  5  T  E  C  O  SCROL  LINES  T  O
; K  P   310  T  5  E  4  R  C   3210   3210  S  E   COMMENTS
---------------------------------------------------------------------------
  C  X   XXX  H  H  X  X  X  L   XXXX   XXXX  H  X   SET INITIALIZE BIT
  C  X   XXX  L  X  X  X  X  L   HHHH   LLLL  L  X   INITIALIZE COUNTERS
  C  L   XXX  L  L  X  X  L  L   HHHH   LLLL  L  X   INITS = L
  C  L   HHH  L  H  X  L  L  L   HHHH   LLLH  L  X   INC LINES, HOLD SCROL
  C  L   HHH  L  H  X  L  L  L   HHHH   LLHL  L  X   INC LINES, HOLD SCROL
  C  L   HHH  L  H  X  L  L  L   HHHH   LLHH  L  X   INC LINES, SCAN = 11
  C  L   HHH  L  H  X  L  L  L   HHHH   LHLL  L  X   INC LINES, SCAN = 11
  C  L   XXX  L  H  X  X  H  L   LLLL   LHLH  L  X   INC LINES & SCROL: LF
  C  L   XXX  L  X  X  X  H  L   LLLH   LHHL  L  X   INC LINES & SCROL: LF
  C  L   XXX  L  L  X  X  L  L   LLLH   LHHL  L  X   HOLD LINES & SCROL
  C  H   XXX  L  L  X  X  L  L   LHHL   LLLH  L  X   SWAP LINES & SCROL
  C  L   XXX  L  X  X  X  H  L   LHHH   LLHL  L  X   INC LINES & SCROL
  C  X   XXX  X  X  L  X  X  L   XXXX   XXXX  X  H   SET OE
  C  X   XXX  X  X  H  X  X  L   XXXX   XXXX  X  L   CLEAR OE
---------------------------------------------------------------------------


DESCRIPTION

"SCROL" AND "LINES" ARE COUNTERS AND POINTERS TO THE RAM. "LINES" IS A
POINTER TO THE LINE THAT IS READ FROM THE RAM. "SCROL" IS A POINTER
TO THE LOCATION IN THE RAM WHERE A NEW LINE CAN BE STORED.  BOTH OF THEM
COUNT UP TO A MAXIMUM OF 16 LINES.

THE BIT "SWAP" ENABLES THE TWO COUNTERS TO TALK TO THE SAME ADDRESS LINES
OF THE RAM.

THE NEXT FIGURE SHOWS ALL THE POINTERS THAT HAVE BEEN DESCRIBED.

"W" MEANS WRITING INTO THE RAM, "R" MEANS READING FROM THE RAM AND "C"
IS A TEMPORARY POINTER.