FeedBackDelay
ptolemy.domains.dde.kernel.FeedBackDelay

FeedBackDelay actors are used to add delay to feedback topologies. If a FeedBackDelay actor consumes a token (real or Null), it has the option of producing an equivalent token on the output with an incremented time stamp value. Alternatively, the FeedBackDelay actor will simply produce the token without altering the time stamp. <P> Two parameters - <I>nullDelay</I> and <I>realDelay</I> - are available for determining whether an FeedBackDelay actor increments the time stamp of produced output tokens. The default value of nullDelay (realDelay) is true (false). If the nullDelay (realDelay) parameter is set to true, then the time stamps of NullTokens (real tokens) will be incremented as they pass through this actor. <P> The delay value that is applied (given that one of the above parameters is true) is determined by the setDelay() and getDelay() methods. More elaborate delay values can be made available by overriding the getDelay() method in derived classes. <P> FeedBackDelay actors are effective for preventing Zeno conditions involving cycles of null tokens. If a DDE model has a feedback topology, a FeedBackDelay actor should be added into the feedback loop. <P> The delay value of a FeedBackDelay actor must be wisely chosen. The delay value should be smaller than any other successive time stamp increment found in a given DDE model. This means that if a particular model might have any two time stamps with time difference delta, then the delay value should be smaller than delta.

Author(s): John S. Davis II
Version:$Id: FeedBackDelay.doc.html,v 1.1 2006/02/22 18:40:27 mangal Exp $
Pt.Proposed Rating:Red (davisj)
Pt.Accepted Rating:Red (yuhong)


input
The input port.
output
The output port.


delay
The delay for this actor. The initial default value is a double with value 1.0.
nullDelay
The boolean parameter that indicates whether a delay value will be added to the time stamp of null tokens that are produced by this actor. This parameter defaults to true.
realDelay
The boolean parameter that indicates whether a delay value will be added to the time stamp of real tokens that are produced by this actor. This parameter defaults to false.