stella/src/emucore/CompuMate.hxx

//============================================================================
//
//   SSSS    tt          lll  lll       
//  SS  SS   tt           ll   ll        
//  SS     tttttt  eeee   ll   ll   aaaa 
//   SSSS    tt   ee  ee  ll   ll      aa
//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
//  SS  SS   tt   ee      ll   ll  aa  aa
//   SSSS     ttt  eeeee llll llll  aaaaa
//
// Copyright (c) 1995-2012 by Bradford W. Mott, Stephen Anthony
// and the Stella Team
//
// See the file "License.txt" for information on usage and redistribution of
// this file, and for a DISCLAIMER OF ALL WARRANTIES.
//
// $Id$
//============================================================================

#ifndef COMPUMATE_HXX
#define COMPUMATE_HXX

#include "bspf.hxx"
#include "Control.hxx"
#include "Event.hxx"

/**
  Cartridge class used for SpectraVideo CompuMate bankswitched games.

  This is more than just a cartridge mapper - it's also a "computer" add-on.  
  There's two 8K EPROMs soldered on top of each other.  There's two short
  wires with DB-9's on them which you plug into the two controller ports.
  A 42 or so key membrane keyboard with audio in and audio out, and 2K of RAM.

  There are 4 4K banks selectable at $1000 - $1FFF, and 2K RAM at
  $1800 - $1FFF (R/W 'line' is available at SWCHA D5, so there's no separate
  read and write ports).

  Bankswitching is done though the controller ports
    SWCHA: D7 = Audio input from tape player
           D6 = Audio out to tape player and 4017 CLK
                1 -> increase key column (0 to 9)
           D5 = 4017 RST, and RAM direction. (high = write, low = read)
                1 -> reset key column to 0 (if D4 = 0)
                0 -> enable RAM writing (if D4 = 1)
           D4 = RAM enable: 1 = disable RAM, 0 = enable RAM
           D3 = keyboard row 1 input (0 = key pressed)
           D2 = keyboard row 1 input (0 = key pressed)
           D1 = bank select high bit
           D0 = bank select low bit

    INPT0: D7 = CTRL key input (0 on startup / 1 = key pressed)
    INPT1: D7 = always HIGH input (pulled high thru 20K resistor)
    INPT2: D7 = always HIGH input (pulled high thru 20K resistor)
    INPT3: D7 = SHIFT key input (0 on startup / 1 = key pressed)
    INPT4: D7 = keyboard row 0 input (0 = key pressed)
    INPT5: D7 = keyboard row 2 input (0 = key pressed)

  The keyboard's composed of a 4017 1 of 10 counter, driving the 10 columns of
  the keyboard.  It has 4 rows.  The 4 row outputs are buffered by inverters.

  Bit 5 of portA controls the reset line on the 4017.  Pulling it high will reset
  scanning to column 0.  Pulling it low will allow the counter to be clocked.

  Bit 6 of portA clocks the 4017.  Each rising edge advances the column one
  count.

  There's 10 columns labelled 0-9, and 4 rows, labelled 0-3.

                           Column

    0     1     2     3     4     5     6     7     8     9
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
  | 7 | | 6 | | 8 | | 2 | | 3 | | 0 | | 9 | | 5 | | 1 | | 4 |  0
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ 
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ 
  | U | | Y | | I | | W | | E | | P | | O | | T | | Q | | R |  1
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+     Row
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
  | J | | H | | K | | S | | D | |ent| | L | | G | | A | | F |  2
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ 
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
  | M | | N | | < | | X | | C | |spc| | > | | B | | Z | | V |  3
  +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ 

  Function and Shift are separate keys that are read by 2 of the paddle inputs.
  These two buttons pull the specific paddle input low when pressed.

  Because the inputs are inverted, a low indicates a pressed button, and a high 
  is an unpressed one.

  The audio input/output are designed to drive a tape player.  The audio output is 
  buffered through an inverter and 2 resistors and a capacitor to reduce the level
  to feed it into the tape player.

  The audio input is passed through a .1uf capacitor and is pulled to 1/2 supply
  by two 20K resistors, then it goes through a hex inverting schmitt trigger to
  square it up.  This then runs into bit 7 of portA.

  This code was heavily borrowed from z26, and uses conventions defined
  there.  Specifically, IOPortA is treated as a complete uInt8, whereas
  the Stella core actually stores this information in boolean arrays
  addressable by DigitalPin number.

  @author  Stephen Anthony & z26 team
  @version $Id$
*/
class CompuMate : public Controller
{
  public:
    /**
      Create a new MindLink controller plugged into the specified jack

      @param jack   The jack the controller is plugged into
      @param event  The event object to use for events
      @param system The system using this controller
    */
    CompuMate(Jack jack, const Event& event, const System& system);

    /**
      Destructor
    */
    virtual ~CompuMate();

  public:
    /**
      Called after *all* digital pins have been written on Port A.
    */
    void controlWrite();

    /**
      Update the entire digital and analog pin state according to the
      events currently set.
    */
    void update();

  private:
    // Internal state of the port pins
    uInt8 myIOPort;
};

#endif