.\" Copyright (c)2004 by Edward Counce, All rights reserved
.\" Copyright (c)2006-2007 by Salvador E. Tropea, All rights reserved
.\" This file is part of drawtiming.
.\"
.\" Drawtiming is free software; you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\"
.\" Drawtiming is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with drawtiming; if not, write to the Free Software
.\" Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
.\"
.Dd April 13, 2005
.Dt DRAWTIMING 1
.Os
.Sh NAME
.Nm drawtiming
.Nd generate timing diagram from signal description
.Sh SYNOPSIS
.Nm
.Op Fl -verbose
.Op Fl -scale Ar factor
.Op Fl -pagesize Ar WxH
.Op Fl -aspect
.Op Fl -cell-height Ar H
.Op Fl -cell-width Ar W
.Op Fl -font-size Ar pts
.Op Fl -line-width Ar W
.Fl -output Ar target
.Ar
.Sh DESCRIPTION
This application provides a command line tool for documenting hardware
and software designs through ideal timing diagrams.  It reads signal
descriptions from a text file with an intuitive syntax, and outputs an
ideal timing diagram to an image file.  Notation typical of timing
diagrams found in the Electrical Engineering discipline is used,
including arrows indicating causal relationships between signal
transitions.
.Pp
The options are as follows:
.Bl -tag -width Fl
.It Fl -help
Show usage reminder.
.It Fl -verbose
Increase diagnostic output.
.It Fl -scale Ar factor
Scale the diagram by the given
.Ar factor .
The default scaling factor is 1.0.
.It Fl -pagesize Ar WidthxHeight
Scale the diagram to fit given image size.
.It Fl -aspect
Maintain fixed aspect ratio if \-\-pagesize given.
.It Fl -cell-height Ar H
Height of the each signal in pixels. Default is 32.
.It Fl -cell-width Ar W
Width for the time unit in pixels. Defaults is 64.
.It Fl -font-size Ar pts
Font size in pts. Default is 18.
.It Fl -line-width Ar W
Line width for drawings in pixels. Default is 1.
.It Fl -output Ar target
The name and format of the output image is determined by
.Ar target .
.It Ar
The input files describe the signals to be diagrammed.  See the
.Sx FILES
and
.Sx EXAMPLES
sections for a description of their format.
.El
.Sh FILES
The following is a technical description of the input file syntax and
semantics.  If you are reading this for the first time, you may want
to skip ahead to the 
.Sx EXAMPLES
section.
.Pp
The input file consists of a series of statements describing the
signal transitions during each clock period of the timing diagram.
Whitespace and comments following a 
.Ql #
are ignored.
.Pp
.Bl -tag -width "SIGNAL=VALUE"
.It SIGNAL=VALUE
This statement changes the value of a signal at the beginning of the
current clock, and adds it to the list of signal dependencies.  The
signal name may consist of one or more words consisting of
alphanumerics and underscores joined by periods, 
.Ql signal.name ,
for example.  The signal value format is described further on.
.It SIGNAL
This statement adds a signal to the list of dependencies without
changing its value.
.El
.Pp
Statements are separated by the following symbols:
.Bl -tag -width "-tD>"
.It ,
The comma separator is used to separate statements without
affecting the dependency list or clock (ie: the next statement will
add to the dependency list).
.It ;
The semicolon separator resets the list of dependencies without
incrementing the clock
.It .
The period separator resets the list of dependencies and
increments the clock.
.It =>
The "causes" separator renders dependency arrows based on the
current list of dependencies and then resets the dependency list.
.It -tD>
The "delay" separator renders a delay arrow from the last dependency
with the annotation 
.Em tD .
.El
.Pp
Signal values are rendered according to the following rules:
.Bl -tag -width "0, 1, true, false"
.It 0 , 1 , true , false
A binary high/low signal.
.It tick
A clock pulse which repeats.
.It pulse
A one-shot clock pulse.
.It X
A don't care value.
.It Z
A tristate value.
.It Qq ABC
Any other alphanumeric token, or text enclosed in quotes is rendered
as a state.  For example, 
.Ql Qq 1 ,
is rendered as a state, whereas,
.Ql 1 ,
is rendered as a high signal.
.El
.Sh EXAMPLES
Let's look at an example input file, and parse its meaning.
.Pp
.Bd -literal -offset indent
POWER=0, FIRE=0, ARMED=0, LED=OFF, COUNT=N.
POWER=1 => LED=GREEN.
FIRE=1. 
FIRE => ARMED=1.
FIRE=0.
FIRE=1.
FIRE, ARMED => LED=RED;
FIRE => COUNT="N+1".
.Ed
.Pp
This input file describes the changes in five signals over a period of
seven clock cycles.  The end of each clock cycle is indicated with a
period.  For example, the following line indicates a single signal,
named
.Ql FIRE
became true during a clock cycle:
.Pp
.Dl FIRE=1.
.Pp
The first clock period of the input file provides the initial value
for all signals to be diagrammed.  The signals will appear on the
timing diagram in the order they first appear in the input file.
Signals are assumed to have the
.Qq don't care
value if their initial value is not given.  
.Pp
Independent signal transitions which occur simultaneously are normally
separated by commas. Since signals aren't normally expected to change
simultaneously, the initial state is a good example of this:
.Pp
.Dl POWER=0, FIRE=0, ARMED=0, LED=OFF, COUNT=N.
.Pp 
Dependencies can also be indicated for a signal transition.
Dependencies are rendered as arrows on the timing diagram from the
last change in each dependency to the dependent signal transition.
Here, the previous change in the state of
.Ql FIRE
causes a change in the 
.Ql ARMED
signal.
.Pp
.Dl FIRE => ARMED=1.
.Pp
To indicate that a change in one signal causes an immediate change in
another signal, list both signal changes in the same clock period:
.Pp
.Dl POWER=1 => LED=GREEN.
.Pp
For signal state changes with multiple dependencies, separate the
dependencies with commas:
.Pp
.Dl FIRE, ARMED => LED=RED.
.Pp
Sometimes, a single dependency causes multiple independent signals to
change.  Use a semicolon to start a new list of dependencies.
Modifying the previous line to indicate that
.Ql FIRE
also causes 
.Ql COUNT
to increment yields:
.Pp
.Dl FIRE, ARMED => LED=RED;
.Dl FIRE => COUNT="N+1".
.Pp
You can find this example and others along with their generated timing
diagrams on the homepage for
.Nm
at
.Ql http://drawtiming.sourceforge.net .
.Sh DIAGNOSTICS
Exit status is 0 on success, and 2 if the command
fails.
.Sh COMPATIBILITY
The
.Nm
command has been tested on FreeBSD, Linux, and Cygwin.
.Sh AUTHORS
This software package was written by
.An Edward Counce Aq ecounce@users.sourceforge.net
Additional modifications by
.An Salvador E. Tropea Aq set@users.sourceforge.net
.An Daniel Beer
.Sh BUGS
None reported.