code: /**
   * Copyright (c) 2013-2014, TU Braunschweig
   * 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.
   */
  package avrora.sim.mcu;
  
  import avrora.sim.InterruptTable;
  import avrora.sim.RWRegister;
  import avrora.sim.Simulator;
  import avrora.sim.state.RegisterUtil;
  import avrora.sim.state.RegisterView;
  import java.util.LinkedList;
  
  /**
   *
   * @author swillenborg
   */
  public class TWI extends AtmelInternalDevice implements InterruptTable.Notification {
  
      final TWBReg TWBR_reg;
      final TWCReg TWCR_reg;
      final TWSReg TWSR_reg;
      final TWDReg TWDR_reg;
      final TWAReg TWAR_reg;
      final TWAMReg TWAMR_reg;
      final LinkedList<TWIDevice> devices = new LinkedList<>();
      final TransferEvent transferEvent = new TransferEvent();
      int interruptNum;
      int clock = 1;
  
      public TWI(AtmelMicrocontroller m) {
          super("twi", m);
          TWBR_reg = new TWBReg();
          TWCR_reg = new TWCReg();
          TWSR_reg = new TWSReg();
          TWDR_reg = new TWDReg();
          TWAR_reg = new TWAReg();
          TWAMR_reg = new TWAMReg();
  
          interruptNum = m.getProperties().getInterrupt("TWI");
  
          installIOReg("TWBR", TWBR_reg);
          installIOReg("TWCR", TWCR_reg);
          installIOReg("TWSR", TWSR_reg);
          installIOReg("TWDR", TWDR_reg);
          installIOReg("TWAR", TWAR_reg);
          installIOReg("TWAMR", TWAMR_reg);
          interpreter.getInterruptTable().registerInternalNotification(this, interruptNum);
  
      }
  
      @Override
      public void force(int inum) {
          
      }
  
      @Override
      public void invoke(int inum) {
          
      }
      enum TransferMode {
          NULL, START, STOP, ADDRESS, DATA_WRITE, DATA_READ;
      };
  
      protected class TransferEvent implements Simulator.Event {
  
          boolean transmitting;
          int status;
          TransferMode mode = TransferMode.NULL;
          
          private byte data;
          private boolean write;
          private boolean rep_start;
          private boolean ack_flag;
  
          protected void enableWriteTransfer(byte data, boolean ack_flag) {
              if (transmitting) {
                  return;
              }
              transmitting = true;
              this.data = data;
              this.ack_flag = ack_flag;
              mode = TransferMode.DATA_WRITE;
              mainClock.insertEvent(this, clock * 7);
      
          }
  
          protected void enableReadTransfer(boolean ack_flag) {
              if (transmitting) {
                  return;
              }
              transmitting = true;
              this.ack_flag = ack_flag;
              mode = TransferMode.DATA_READ;
              mainClock.insertEvent(this, clock * 7);
          }
  
          protected void enableAddressTransfer(byte address, boolean write, boolean rep_start, boolean ack_flag) {
              //(byte) (TWDR_reg.value & 0xfe), write, rep, ack_flag);
              if (transmitting) {
                  return;
              }
              transmitting = true;
              this.data = address;
              this.write = write;
              this.rep_start = rep_start;
              this.ack_flag = ack_flag;
              mode = TransferMode.ADDRESS;
              mainClock.insertEvent(this, clock * 7);
              
          }
  
          protected void enableStopTransfer() {
              if (transmitting) {
                  return;
              }
              transmitting = true;
              mode = TransferMode.STOP;
              mainClock.insertEvent(this, clock * 2);
              
          }
          protected void enableStartTransfer(int status) {
              if (transmitting) {
                  return;
              }
              transmitting = true;
              this.status = status;
              mode = TransferMode.START;
              mainClock.insertEvent(this, clock * 2);
          }
  
          @Override
          public void fire() {
              if (!transmitting) {
                  return;
              }
              Boolean ack = null;
              switch (mode) {
                  case NULL:
                      break;
                  case START:
                      TWSR_reg.setStatus(status);
                      TWCR_reg.setValue(TWCR_reg.value | (1 << TWCReg.TWINT));
                      break;
                  case STOP:
                      for (TWIDevice dev : devices) {
                          dev.stop();
                      }
                      TWCR_reg.setValue(TWCR_reg.value & ~(1 << TWCReg.TWSTO));
                      break;
                  case ADDRESS:
                      
                      for (TWIDevice dev : devices) {
                          Boolean dev_ack = dev.start(data, write, rep_start, ack_flag);
                          if (dev_ack != null) {
                              ack = dev_ack;
                          }
                      }
                      if (ack != null) {
                          if (write) {
                              if (ack) {
                                  TWSR_reg.setStatus(TWSReg.TWI_STATUS_SLA_W_ACK);
                              } else {
                                  TWSR_reg.setStatus(TWSReg.TWI_STATUS_SLA_W_NACK);
                              }
                          } else {
                              if (ack) {
                                  TWSR_reg.setStatus(TWSReg.TWI_STATUS_SLA_R_ACK);
                              } else {
                                  TWSR_reg.setStatus(TWSReg.TWI_STATUS_SLA_R_NACK);
                              }
                          }
                      }
                      TWCR_reg.setValue(TWCR_reg.value | (1 << TWCReg.TWINT));
                      break;
                  case DATA_READ:
                      Byte result = null;
                      for (TWIDevice dev : devices) {
                          TWIData result_data = dev.readByte(ack_flag);
                          if (result_data != null) {
                              ack = result_data.ack;
                              result = result_data.data;
                          }
                      }
                      if (result != null) {
                          TWDR_reg.setValue(result);
                      }
                      if (ack != null) {
                          if (ack) {
                              TWSR_reg.setStatus(TWSReg.TWI_STATUS_DATA_R_ACK);
                          } else {
                              TWSR_reg.setStatus(TWSReg.TWI_STATUS_DATA_R_NACK);
                          }
                      }
                      TWCR_reg.setValue(TWCR_reg.value | (1 << TWCReg.TWINT));
                      break;
                  case DATA_WRITE:
                      for (TWIDevice dev : devices) {
                          Boolean dev_ack = dev.writeByte(data, ack_flag);
                          if (dev_ack != null) {
                              ack = dev_ack;
                          }
                      }
                      if (ack != null) {
                          if (ack) {
                              TWSR_reg.setStatus(TWSReg.TWI_STATUS_DATA_W_ACK);
                          } else {
                              TWSR_reg.setStatus(TWSReg.TWI_STATUS_DATA_W_NACK);
                          }
                      }
                      TWCR_reg.setValue(TWCR_reg.value | (1 << TWCReg.TWINT));
                      break;
                  default:
              }
              mode = TransferMode.NULL;
              transmitting = false;
          }
      }
  
      /**
       * TWCR - TWI Control Register
       */
      private class TWCReg extends RWRegister {
  
          static final int TWINT = 7;
          static final int TWEA = 6;
          static final int TWSTA = 5;
          static final int TWSTO = 4;
          static final int TWWC = 3;
          static final int TWEN = 2;
          static final int TWIE = 0;
          static final int write_mask = 0xf5;
          /**
           * TWINT: TWI Interrupt Flag
           */
          final RegisterView _interrupt = RegisterUtil.bitView(this, TWINT);
          /**
           * TWEA: TWI Enable Acknowledge Bit
           */
          final RegisterView _enable_ack = RegisterUtil.bitView(this, TWEA);
  
          /**
           * TWSTA: TWI START Condition Bit
           */
          final RegisterView _start = RegisterUtil.bitView(this, TWSTA);
  
          /**
           * TWSTO: TWI STOP Condition Bit
           */
          final RegisterView _stop = RegisterUtil.bitView(this, TWSTO);
  
          /**
           * TWWC: TWI Write Collision Flag
           */
          final RegisterView _write_collision = RegisterUtil.bitView(this, TWWC);
  
          /**
           * TWEN: TWI: Enable Bit
           */
          final RegisterView _enable = RegisterUtil.bitView(this, TWEN);
  
          /**
           * TWIE: TWI Interrupt Enable Bit
           */
          final RegisterView _interrupt_enable = RegisterUtil.bitView(this, TWIE);
  
          public TWCReg() {
              setValue(0x00);
          }
          boolean started = false;
          boolean rep_start = false;
          boolean next_is_addr = false;
          boolean write_mode = false;
  
          @Override
          public void write(byte val) {
              // Bits 1 and 3 are read-only
              val = (byte) ((this.value & ~write_mask) | (val & write_mask));
  
              if ((val & (1 << TWINT)) != 0) {
                  val &= ~(1 << TWINT);
              }
              super.write(val);
              
              if (_enable.getValue() != 0) {
                  if (_start.getValue() != 0) {
                      if (!started) {
                          transferEvent.enableStartTransfer(TWSReg.TWI_STATUS_START);
                          started = true;
                      } else {
                          transferEvent.enableStartTransfer(TWSReg.TWI_STATUS_START_REP);
                      }
                      next_is_addr = true;
                  } else if (_stop.getValue() != 0) {
                      transferEvent.enableStopTransfer();
                      started = false;
                  } else {
                      boolean ack_flag = (_enable_ack.getValue() != 0);
                      if (next_is_addr) {
                          next_is_addr = false;
                          write_mode = ((TWDR_reg.value & 1) == 0);
                          transferEvent.enableAddressTransfer((byte) (TWDR_reg.value & 0xfe), write_mode, rep_start, ack_flag);
                          rep_start = true;
                      } else {
                          if (write_mode) {
                              transferEvent.enableWriteTransfer(TWDR_reg.value, ack_flag);
                          } else {
                              transferEvent.enableReadTransfer(ack_flag);
                          }
                      }
                      
                  }
              }
          }
      }
  
      /**
       * TWSR - TWI Status register
       */
      private class TWSReg extends RWRegister {
  
          /**
           * Bus error due to an illegal START or STOP condition
           */
          static final int TWI_STATUS_ERROR = 0x0;
  
          /**
           * A START condition has been transmitted
           */
          static final int TWI_STATUS_START = 0x8;
  
          /**
           * A repeated START condition has been transmitted
           */
          static final int TWI_STATUS_START_REP = 0x10;
  
          /**
           * SLA+W has been transmitted; ACK has been received
           */
          static final int TWI_STATUS_SLA_W_ACK = 0x18;
  
          /**
           * SLA+W has been transmitted; NOT ACK has been received
           */
          static final int TWI_STATUS_SLA_W_NACK = 0x20;
  
          /**
           * Data byte has been transmitted; ACK has been received
           */
          static final int TWI_STATUS_DATA_W_ACK = 0x28;
  
          /**
           * Data byte has been transmitted; NOT ACK has been received
           */
          static final int TWI_STATUS_DATA_W_NACK = 0x30;
  
          /**
           * Arbitration lost in SLA+W or data bytes
           */
          static final int TWI_STATUS_ARBITRATION_LOST = 0x38;
  
          /**
           * SLA+R has been transmitted; ACK has been received
           */
          static final int TWI_STATUS_SLA_R_ACK = 0x40;
  
          /**
           * SLA+R has been transmitted; NOT ACK has been received
           */
          static final int TWI_STATUS_SLA_R_NACK = 0x48;
  
          /**
           * Data byte has been received; ACK has been returned
           */
          static final int TWI_STATUS_DATA_R_ACK = 0x50;
  
          /**
           * Data byte has been received; NOT ACK has been returned
           */
          static final int TWI_STATUS_DATA_R_NACK = 0x58;
  
          /**
           * Own SLA+W has been received; ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_SLA_W_ACK = 0x60;
  
          /**
           * Arbitration lost in SLA+R/W as Master; own SLA+W has been received;
           * ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_SLA_W_ACK_ARBITRATION_LOST = 0x68;
  
          /**
           * General call address has been received; ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_ADDRESS_ACK = 0x70;
  
          /**
           * Arbitration lost in SLA+R/W as Master; General call address has been
           * received; ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_ADDRESS_ACK_ARBITRATION_LOST = 0x78;
  
          /**
           * Previously addressed with own SLA+W; data has been received; ACK has
           * been returned
           */
          static final int TWI_STATUS_SLAVE_SLA_W_ADDRESSED_ACK = 0x80;
  
          /**
           * Previously addressed with own SLA+W; data has been received; NOT ACK
           * has been returned
           */
          static final int TWI_STATUS_SLAVE_SLA_W_ADDRESSED_NACK = 0x88;
  
          /**
           * Previously addressed with general call; data has been received; ACK
           * has been returned
           */
          static final int TWI_STATUS_SLAVE_GENERAL_DATA_ACK = 0x90;
  
          /**
           * Previously addressed with general call; data has been received; NOT
           * ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_GENERAL_DATA_NACK = 0x98;
  
          /**
           * A STOP condition or repeated START condition has been received while
           * still addressed as Slave
           */
          static final int TWI_STATUS_SLAVE_STOP_OR_REP_START = 0xa0;
  
          /**
           * Own SLA+R has been received; ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_SLA_R_ACK = 0xa8;
  
          /**
           * Arbitration lost in SLA+R/W as Master; own SLA+R has been received;
           * ACK has been returned
           */
          static final int TWI_STATUS_SLAVE_SLA_R_ACK_ARBITRATION_LOST = 0xb0;
  
          /**
           * Data byte in TWDR has been transmitted; ACK has been received
           */
          static final int TWI_STATUS_SLAVE_TWDR_SENT_ACK = 0xb8;
  
          /**
           * Data byte in TWDR has been transmitted; NOT ACK has been received
           */
          static final int TWI_STATUS_SLAVE_TWDR_SENT_NACK = 0xc0;
  
         
          /**
           * No relevant state information available; TWINT = “0”
           */
          static final int TWI_STATUS_DEFAULT = 0xf8;
  
  
          static final int TWS7 = 7;
          static final int TWS6 = 6;
          static final int TWS5 = 5;
          static final int TWS4 = 4;
          static final int TWS3 = 3;
  
          static final int TWPS1 = 1;
          static final int TWPS0 = 0;
  
          final RegisterView _twps = RegisterUtil.bitRangeView(this, TWPS0, TWPS1);
  
          static final int write_mask = 0x03;
  
          public TWSReg() {
              setValue(TWI_STATUS_DEFAULT);
          }
  
          @Override
          public void write(byte val) {
              // only bits 0 and 1 are writeable
              super.write((byte) ((this.value & ~write_mask) | (val & write_mask)));
              updateClock();
          }
  
          public void setStatus(int status) {
              setValue((status | (0x03 & this.value)));
          }
  
      }
  
      /**
       * TWDR - TWI Data Register
       */
      private class TWDReg extends RWRegister {
  
          static final int TWD7 = 7;
          static final int TWD6 = 6;
          static final int TWD5 = 5;
          static final int TWD4 = 4;
          static final int TWD3 = 3;
          static final int TWD2 = 2;
          static final int TWD1 = 1;
          static final int TWD0 = 0;
  
          public TWDReg() {
              setValue(0xFF);
          }
      }
  
      /**
       * TWI - TWI (Slave) Address Register
       */
      private class TWAReg extends RWRegister {
          static final int TWA6 = 7;
          static final int TWA5 = 6;
          static final int TWA4 = 5;
          static final int TWA3 = 4;
          static final int TWA2 = 3;
          static final int TWA1 = 2;
          static final int TWA0 = 1;
          static final int TWGCE = 0;
          
          public TWAReg() {
              setValue(0xFE);
          }
      }
  
      /**
       * TWAMR - TWI (slave) Address Mask Register
       */
      private class TWAMReg extends RWRegister {
          static final int TWAM6 = 7;
          static final int TWAM5 = 6;
          static final int TWAM4 = 5;
          static final int TWAM3 = 4;
          static final int TWAM2 = 3;
          static final int TWAM1 = 2;
          static final int TWAM0 = 1;
  
          static final int write_mask = 0xFE;
          public TWAMReg() {
              setValue(0x00);
          }
  
          @Override
          public void write(byte val) {
              // bit 0 is read only
              super.write((byte) ((this.value & ~write_mask) | (val & write_mask)));
          }
  
      }
  
      /**
       * TWBR - TWI Bit Rate Register
       */
      class TWBReg extends RWRegister {
          static final int TWBR7 = 7;
          static final int TWBR6 = 6;
          static final int TWBR5 = 5;
          static final int TWBR4 = 4;
          static final int TWBR3 = 3;
          static final int TWBR2 = 2;
          static final int TWBR1 = 1;
          static final int TWBR0 = 0;
  
          public TWBReg() {
              setValue(0x00);
          }
  
          @Override
          public void write(byte val) {
              super.write(val);
              updateClock();
          }
  
      }
  
      private void updateClock() {
          int twps = TWSR_reg._twps.getValue();
          int twbr = TWBR_reg.getValue();
          clock = 16 + 2 * (twbr) << (2 * twps);
      }
  
      public void connect(TWIDevice device) {
          if (!devices.contains(device)) {
              devices.add(device);
          }
      }
  }
  