Name       6502_DECODER;
Partno     Lattice22V10B;
Date       02/04/15;
Revision   01;
Designer   shalewyn.com;
Company    shalewyn.com;
Assembly   XXXXX;
Location   XXXXX;
Device     g22v10;


/*
 * Lattice GAL 22V10B pinout, DIP, top view
 * 
 * I/CLK.[ 1     24 ].VCC
 *   I.[ 2     23 ].I/O/Q
 *   I.[ 3     22 ].I/O/Q
 *   I.[ 4     21 ].I/O/Q
 *   I.[ 5     20 ].I/O/Q
 *   I.[ 6     19 ].I/O/Q
 *   I.[ 7     18 ].I/O/Q
 *   I.[ 8     17 ].I/O/Q
 *   I.[ 9     16 ].I/O/Q
 *   I.[ 10    15 ].I/O/Q
 *   I.[ 11    14 ].I/O/Q
 * GND.[ 12    13 ].I
 *
 *
 *
 * $1000-$1FFF   -   %0000 0000 0000 0000 - %0001 1111 1111 1111
 * $2000-$7FFF   -   %0010 0000 0000 0000 - %0111 1111 1111 1111
 * $8000-$800F   -   %1000 0000 0000 0000 - %1000 0000 0000 1111
 * $8010-$801F   -   %1000 0000 0001 0000 - %1000 0000 0001 1111
 * $8020-$802F   -   %1000 0000 0010 0000 - %1000 0000 0010 1111
 * $8040-$804F   -   %1000 0000 0100 0000 - %1000 0000 0100 1111
 * $9000-$FFFF   -   %1001 0000 0000 0000 - %1111 1111 1111 1111
 *
 *
 * !Pin 17 - non-swap RAM   $0000-$1FFF
 * !Pin 18 - Swap bank 0  - $2000-$7FFF
 * !Pin 19 - Swap bank 1  - $2000-$7FFF
 * !Pin 21 - /VIA 1       - $8000-$800F
 * !Pin 22 - /VIA 2       - $8010-$801F
 * !Pin 23 - /ROM         - $9000-$FFFF
 * 
 * 
 * Inputs
 */

/* Inputs */

PIN 1      = PHI2;
PIN 2      = R_W;
PIN [3..6] = [A15..12];
PIN [7..9] = [A6..4];
PIN 10     = sb0;
PIN 11     = sb1;

/* Outputs */

PIN 14     = !RD;
PIN 15     = !WR;
 
PIN 16     = !VIA1;
PIN 17     = !VIA2;
PIN 18     = !BASERAM;
PIN 19     = !SWAPBANK0;
PIN 20     = !SWAPBANK1;
PIN 21     = !SWAPBANK2;
PIN 22     = !SWAPBANK3;
PIN 23     = !ROM;

/* Rules */

RD    = PHI2 &  R_W;
WR    = PHI2 & !R_W;

BASERAM   =   !A15 & !A14 & !A13 & !A12;

SWAPBANK0   =   !A15 & !A14 &  A13 & !A12 & !sb0 & !sb1
       # !A15 & !A14 &  A13 &  A12 & !sb0 & !sb1
      # !A15 &  A14 & !A13 & !A12 & !sb0 & !sb1
      # !A15 &  A14 & !A13 &  A12 & !sb0 & !sb1
      # !A15 &  A14 &  A13 & !A12 & !sb0 & !sb1
      # !A15 &  A14 &  A13 &  A12 & !sb0 & !sb1;

SWAPBANK1   =   !A15 & !A14 &  A13 & !A12 & !sb0 & sb1
       # !A15 & !A14 &  A13 &  A12 & !sb0 & sb1
      # !A15 &  A14 & !A13 & !A12 & !sb0 & sb1
      # !A15 &  A14 & !A13 &  A12 & !sb0 & sb1
      # !A15 &  A14 &  A13 & !A12 & !sb0 & sb1
      # !A15 &  A14 &  A13 &  A12 & !sb0 & sb1;

SWAPBANK2   =   !A15 & !A14 &  A13 & !A12 & sb0 & !sb1
       # !A15 & !A14 &  A13 &  A12 & sb0 & !sb1
      # !A15 &  A14 & !A13 & !A12 & sb0 & !sb1
      # !A15 &  A14 & !A13 &  A12 & sb0 & !sb1
      # !A15 &  A14 &  A13 & !A12 & sb0 & !sb1
      # !A15 &  A14 &  A13 &  A12 & sb0 & !sb1;

SWAPBANK3   =   !A15 & !A14 &  A13 & !A12 & !sb0 & sb1
       # !A15 & !A14 &  A13 &  A12 & sb0 & sb1
      # !A15 &  A14 & !A13 & !A12 & sb0 & sb1
      # !A15 &  A14 & !A13 &  A12 & sb0 & sb1
      # !A15 &  A14 &  A13 & !A12 & sb0 & sb1
      # !A15 &  A14 &  A13 &  A12 & sb0 & sb1;

VIA1   =  A15 & !A14 & !A13 & !A12 & !A5 & !A4;
VIA2   =  A15 & !A14 & !A13 & !A12 & !A5 &  A4;

ROM   =  A15 & !A14 & !A13 &  A12
   #  A15 & !A14 &  A13 & !A12
   #  A15 & !A14 &  A13 &  A12
   #  A15 &  A14 & !A13 & !A12
   #  A15 &  A14 & !A13 &  A12
   #  A15 &  A14 &  A13 & !A12
   #  A15 &  A14 &  A13 &  A12;