code: /**
   * Copyright (c) 2005, Regents of the University of California
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * Redistributions of source code must retain the above copyright notice,
   * this list of conditions and the following disclaimer.
   *
   * Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * Neither the name of the University of California, Los Angeles nor the
   * names of its contributors may be used to endorse or promote products
   * derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * Creation date: Nov 14, 2005
   */
  
  package avrora.sim;
  
  import avrora.arch.AbstractInstr;
  
  /**
   * @author Ben L. Titzer
   */
  public interface State {
  
      /**
       * The <code>getSP()</code> method reads the current value of the stack pointer. Since the stack pointer
       * is stored in two IO registers, this method will cause the invocation of the <code>.read()</code> method
       * on each of the <code>IOReg</code> objects that store these values.
       *
       * @return the value of the stack pointer as a byte address
       */
      int getSP();
  
      /**
       * The <code>getPC()</code> retrieves the current program counter.
       *
       * @return the program counter as a byte address
       */
      int getPC();
  
      /**
       * The <code>getCycles()</code> method returns the clock cycle count recorded so far in the simulation.
       *
       * @return the number of clock cycles elapsed in the simulation
       */
      long getCycles();
  
      /**
       * The <code>getSimulator()</code> method returns the simulator associated with this state
       * instance.
       * @return a reference to the simulator associated with this state instance.
       */
      Simulator getSimulator();
  
      /**
       * The <code>getInstr()</code> can be used to retrieve a reference to the <code>AbstractInstr</code> object
       * representing the instruction at the specified program address.
       *
       * @param address the byte address from which to read the instruction
       * @return a reference to the <code>AbstractInstr</code> object representing the instruction at that address in
       *         the program
       */
      public AbstractInstr getInstr(int address);
  }
  