Subversion Repositories openrisc_2011-10-31

// ----------------------------------------------------------------------------
 
// The TAP state machine: definition
 
// Copyright (C) 2009  Embecosm Limited <info@embecosm.com>
 
// Contributor Jeremy Bennett <jeremy.bennett@embecosm.com>
 
// This file is part of the Embecosm cycle accurate SystemC JTAG library.
 
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or (at your
// option) any later version.
 
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
// License for more details.
 
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
// ----------------------------------------------------------------------------
 
// $Id$
 
#ifndef TAP_STATE_MACHINE__H
#define TAP_STATE_MACHINE__H
 
//! Enumeration of all the states in the TAP state machine.
 
//! Last entry is not a state, but a marker of the number of states. Useful
//! for state transition matrices.
enum TapState {
  TAP_TEST_LOGIC_RESET =  0,
  TAP_RUN_TEST_IDLE    =  1,
  TAP_SELECT_DR_SCAN   =  2,
  TAP_CAPTURE_DR       =  3,
  TAP_SHIFT_DR         =  4,
  TAP_EXIT1_DR         =  5,
  TAP_PAUSE_DR         =  6,
  TAP_EXIT2_DR         =  7,
  TAP_UPDATE_DR        =  8,
  TAP_SELECT_IR_SCAN   =  9,
  TAP_CAPTURE_IR       = 10,
  TAP_SHIFT_IR         = 11,
  TAP_EXIT1_IR         = 12,
  TAP_PAUSE_IR         = 13,
  TAP_EXIT2_IR         = 14,
  TAP_UPDATE_IR        = 15,
  TAP_SIZE             = 16
 
};	// enum TapState
 
 
//! Textual representation of all the TAP states.
 
//! Provided for debugging purposes
static const char *tapStateNames[TAP_SIZE] = {
  "Test-Logic-Reset",
  "Run-Test/Idle",
  "Select-DR-Scan",
  "Capture-DR",
  "Shift-DR",
  "Exit1-DR",
  "Pause-DR",
  "Exit2-DR",
  "Update-DR",
  "Select-IR-Scan",
  "Capture-IR",
  "Shift-IR",
  "Exit1-IR",
  "Pause-IR",
  "Exit2-IR",
  "Update-IR"
 
};	// tapStateNames
 
 
//! TAP state machine
 
//! Tracks the state of the TAP. This should mirror the state of the TAP in
//! the connected HW.
 
//! The state machine is created in the reset condition, but in truth we
//! cannot know what the state is. It is essential the TAP is reset before
//! first being used.
 
//! We cannot know for certain when the TAP state machine has been reset. 5
//! consecutive TMS=1 transitions will take you there, but a reset of the
//! target could undo this. It is the responsibility of the user of the TAP
//! state machine.
 
//! For convenience of users, this class provides a flag (resetDone::),
//! with accessors by which reset state can be recorded.
 
 
class TapStateMachine
{
public:
 
  friend class  JtagSC;
  friend class  TapAction;
  friend class  TapActionDRScan;
  friend class  TapActionIRScan;
  friend class  TapActionReset;
 
 
protected:
 
  //! The number of cycles of TMS=1 required to force reset
  static const int TAP_RESET_CYCLES = 5;
 
  // Constructor
  TapStateMachine();
 
  // Accessor for TAP state
  TapState  getState ();
 
  // Accessors for TAP reset state
  bool  getResetDone ();
  void  setResetDone (bool  _resetState);
 
  // Drive the TAP state machine
  void  nextState (bool tms);
 
  // Determine if we are in a particular target state
  bool  targetState (TapState  target,
		     bool     &tms);
 
private:
 
  //! The current TAP state
  TapState  state;
 
  //! True if the TAP state machine has been through a reset.
 
  //! The state can be sure to match that of the target. Responsibility of
  //! user classes to set this.
  bool  resetDone;
 
};	// class TapStateMachine
 
 
#endif	// TAP_STATE_MACHINE__H