Copyright (c) 1993 Ohio Board of Regents and the University of
Cincinnati.  All Rights Reserved.

author: sidhartha mohanty.
smohanty@thor.ece.uc.edu

This directory contains the tar file of a package, package body, 
and design entities (with corresponding architectures) to support 
the construction and evaluation of Queues.  The basic goal of this 
effort was to simplify the construction of Queueing networks in 
vhdl by providing constructs as close to those of general Queueing 
models as possible.

The design entities are: source, queue, server, join, fork, sink, and
the delay entity.  The generation parameters of the source, the service
time distributions of the server, the distributions of the fork unit,
and the delay time distributions are controlled by invoking a random
number distribution.  Various random number distributions are available
in the file rand.vhdl (written by G. Swaminathan of the University of
Virginia).  The mean and variance for the various distributions (wherever
required) are specified by the real number pair in the generic "generation".
The inputs to frequency are different for the different types of distributions
and they should be specified accordingly or default fixed values could be 
used instead. For the Uniform distribution, the mean would be infact the
lower limit of the distribution and the var the upper limit. For the Normal 
distribution they are what they mean exactly. For the Poisson distribution 
the mean is specified and the var value is not used.  The mean has to be <= 1.0,
and seed <= 1.  For the Fixed distribution, the mean is the average time
between the generation of two tokens, in fs.  All the values specified for mean 
and var should be >= 0.

Extensive debugging facility is provided. The various options for debug
messages can be specified by changing the generic parameter "debug_control".

Various performance statistics relevant to the Queueing models are also
obtained.  Examples are average queue length, average service time, average
throughput, etc..  These statistics are generated into a file specified by
the user in the generic parameter: "file_name" and the stats are generated
at a frequency specified by the user in the generic: "report_freq".

This system has been tested using the Synopsys simulator version 3.0b.

Some of the examples of the Queueing models constructed and simulated using
these VHDL Queueing libraries are also available in this dir: test*.vhdl,
closed12.vhdl.   For more details of the VHDL Queueing libraries and the
examples refer to the thesis:
S. Mohanty. "An Integrated Design Environment for Rapid System 
Prototyping, Performance Modeling and Analysis using VHDL", September,
1994, available through Mosaic at 
href="http://www.ece.uc.edu/~smohanty/homepage.html".

enjoy,

Sidhartha Mohanty
10/30/94.

P.S.: Bug reports to smohanty@thor.ece.uc.edu.