old_contents: ''' Copyright (c) 2013 Potential Ventures Ltd
  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 Potential Ventures Ltd 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 POTENTIAL VENTURES LTD 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. '''
  
  """
      A clock class
  """
  import simulator
  
  from cocotb.log import SimLog
  
  class BaseClock(object):
      """Base class to derive from"""
      def __init__(self, signal):
          self.signal = signal
          self.log = SimLog("cocotb.%s.%s" % (self.__class__.__name__, self.signal.name))
  
  class Clock(BaseClock):
      """
      simple 50:50 duty cycle clock
      """
      def __init__(self, signal, period):
          BaseClock.__init__(self, signal)
          self.period = period
          self.frequency = 1.0 / period * 1000000
          self.hdl = None
  
  
      def start(self, cycles=0):
          """
          cycles = 0 will not auto stop the clock
          """
          if self.hdl is None:
              self.hdl = simulator.create_clock(self.signal._handle, self.period, cycles)
              self.log.debug("Clock %s Started with period %d" % (str(self.signal), self.period))
          else:
              self.log.warning("Clock %s already started" % (str(self.signal)))
  
      def stop(self):
          if self.hdl is not None:
              simulator.stop_clock(self.hdl)
  
      def __str__(self):
          return self.__class__.__name__ + "(%3.1fMHz)" % self.frequency
  
new_contents: ''' Copyright (c) 2013 Potential Ventures Ltd
  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 Potential Ventures Ltd 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 POTENTIAL VENTURES LTD 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. '''
  
  """
      A clock class
  """
  import simulator
  
  from cocotb.log import SimLog
  
  class BaseClock(object):
      """Base class to derive from"""
      def __init__(self, signal):
          self.signal = signal
          self.log = SimLog("cocotb.%s.%s" % (self.__class__.__name__, self.signal.name))
  
  class Clock(BaseClock):
      """
      simple 50:50 duty cycle clock
      """
      def __init__(self, signal, period):
          BaseClock.__init__(self, signal)
          self.period = period
          self.frequency = 1.0 / period * 1000000
          self.hdl = None
  
  
      def start(self, cycles=0):
          """
          cycles = 0 will not auto stop the clock
          """
          if self.hdl is None:
              self.hdl = simulator.create_clock(self.signal._handle, self.period, cycles)
              self.log.info("Clock %s Started with period %d" % (str(self.signal), self.period))
          else:
              self.log.debug("Clock %s already started" % (str(self.signal)))
  
      def stop(self):
          if self.hdl is not None:
              simulator.stop_clock(self.hdl)
  
      def __str__(self):
          return self.__class__.__name__ + "(%3.1fMHz)" % self.frequency
  
subject: Adjust Clock message severities