
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.