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// ----------------------------------------------------------------------------

// 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 ()