Subversion Repositories openrisc_2011-10-31

// ----------------------------------------------------------------------------
 
// TAP IR-Scan action: implementation
 
// 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/>.
 
// The C/C++ parts of this program are commented throughout in a fashion
// suitable for processing with Doxygen.
 
// ----------------------------------------------------------------------------
 
// $Id$
 
 
#include "TapActionIRScan.h"
#include "TapStateMachine.h"
 
 
//! Constructor
 
//! Sets up the superclass with the SystemC completion event and initializes
//! our state as appropriate.
 
//! @param[in] doneEvent  SystemC event to be signalled when this action is
//!                       complete.
//! @param[in] _iRegIn    The register to shift in.
//! @param[in] _iRegSize  Size in bits of the register to shift in.
 
TapActionIRScan::TapActionIRScan (sc_core::sc_event *_doneEvent,
				  uint32_t           _iRegIn,
				  int                _iRegSize) :
  TapAction (_doneEvent),
  iRegIn (_iRegIn),
  iRegSize (_iRegSize),
  iRegOut (0),
  bitsShifted (0),
  iRScanState (SHIFT_IR_PREPARING)
{
 
}	// TapActionIRScan ()
 
 
//! Process the Shift-IR action
 
//! This drives the IR-Scan state. We can only do this if we have the TAP
//! state machine in a consistent state, which in turn is only possible if we
//! have been through a reset cycle.
 
//! If the state machine shows it has yet to be through a reset cycle, we
//! drive that cycle, after issuing a warning. This functionality is provided
//! by the parent class, TapAction::.
 
//! @param[in]  tapStateMachine  The TAP state machine with which this action
//!                              is associated. 
//! @param[out] tdi              The value to drive on TDI
//! @param[in]  tdo              The value currently on TDO
//! @param[out] tms              The value to drive on TMS
 
//! @return  True if the action is complete
 
bool
TapActionIRScan::process (TapStateMachine *tapStateMachine,
			  bool            &tdi,
			  bool             tdo,
			  bool            &tms)
{
  // Ensure we are in a consistent state. If not then we'll have moved towards
  // it and can return with the given tms
  if (!checkResetDone (tapStateMachine, tms, true))
    {
      return false;
    }
 
  // We are consistent, so work through the IR-Scan process
  switch (iRScanState)
    {
    case SHIFT_IR_PREPARING:
 
      // Are we in the Shift-IR state yet?
      if (!tapStateMachine->targetState (TAP_SHIFT_IR, tms))
	{
	  return  false;		// Not there. Accept the TMS value
	}
      else
	{
	  iRScanState = SHIFT_IR_SHIFTING;	// Drop through
	}
 
    case SHIFT_IR_SHIFTING:
 
      // Are we still shifting stuff?
      if (bitsShifted < iRegSize)
	{
	  // We are in the Shift-IR state. Another bit about to be done, so
	  // increment the count
	  bitsShifted++;
 
	  // Shift out the TDI value from the bottom of the register
	  tdi       = iRegIn & 1;
	  iRegIn >>= 1;
 
	  // Record the TDO value. This is always a cycle late, so we ignore
	  // it the first time. The value shifts in from the top.
	  if (bitsShifted > 1)
	    {
	      iRegOut >>= 1;		// Move all the existing bits right
 
	      if (tdo)			// OR any new bit in
		{
		  uint32_t tmpBit = 1 << (iRegSize - 1);
		  iRegOut |= tmpBit;
		}
	    }
 
	  // TMS is 0 to keep us here UNLESS this is the last bit, in which
	  // case it is 1 to move us into Exit1-IR.
	  tms = (bitsShifted == iRegSize);
 
	  return false;
	}
      else
	{
	  // Capture the last TDO bit
	  iRegOut >>= 1;		// Move all the existing bits right
 
	  if (tdo)			// OR any new bit in
	    {
	      uint32_t tmpBit = 1 << (iRegSize - 1);
	      iRegOut |= tmpBit;
	    }
 
	  iRScanState = SHIFT_IR_UPDATING;	// Drop through
	}
 
    case SHIFT_IR_UPDATING:
 
      // Are we still trying to update?
      if (!tapStateMachine->targetState (TAP_UPDATE_IR, tms))
	{
	  return  false;		// Not there. Accept the TMS value
	}
      else
	{
	  return  true;			// All done
	}
    }
}	// process ()
 
 
//! Get the shifted out register
 
//! @return  The value of the shifted our register
 
uint32_t
TapActionIRScan::getIRegOut ()
{
  return  iRegOut;
 
}	// getIRegOut ()