NAME
drawtiming - generate timing diagram from signal description
SYNOPSIS
drawtiming [--verbose] [--scale factor] [--pagesize WxH] [--aspect]
[--cell-height H] [--cell-width W] [--font-size pts]
[--line-width W] --output target file ...
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.
The options are as follows:
--help Show usage reminder.
--verbose Increase diagnostic output.
--scale factor
Scale the diagram by the given factor. The default scaling
factor is 1.0.
--pagesize WidthxHeight
Scale the diagram to fit given image size.
--aspect Maintain fixed aspect ratio if --pagesize given.
--cell-height H
Height of the each signal in pixels. Default is 32.
--cell-width W
Width for the time unit in pixels. Defaults is 64.
--font-size pts
Font size in pts. Default is 18.
--line-width W
Line width for drawings in pixels. Default is 1.
--output target
The name and format of the output image is determined by
target.
file ... The input files describe the signals to be diagrammed. See
the FILES and EXAMPLES sections for a description of their
format.
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 EXAMPLES section.
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 ‘#’ are ignored.
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, ‘signal.name’, for example. The signal
value format is described further on.
SIGNAL This statement adds a signal to the list of dependencies
without changing its value.
Statements are seperated by the following symbols:
, The comma seperator is used to seperate statements without
affecting the dependency list or clock (ie: the next statement will
add to the dependency list).
; The semicolon seperator resets the list of dependencies without
incrementing the clock
. The period seperator resets the list of dependencies and increments
the clock.
=> The "causes" seperator renders dependency arrows based on the
current list of dependencies and then resets the dependency list.
-tD> The "delay" seperator renders a delay arrow from the last
dependency with the annotation tD.
Signal values are rendered according to the following rules:
0, 1, true, false A binary high/low signal.
tick A clock pulse which repeats.
pulse A one-shot clock pulse.
X A don’t care value.
Z A tristate value.
"ABC" Any other alphanumeric token, or text enclosed in
quotes is rendered as a state. For example, ‘"1"’, is
rendered as a state, whereas, ‘1’, is rendered as a
high signal.
EXAMPLES
Let’s look at an example input file, and parse its meaning.
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".
This input file descibes 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
‘FIRE’ became true during a clock cycle:
FIRE=1.
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 "don’t care" value if their initial value is not
given.
Independent signal transitions which occur simultaneously are normally
seperated by commas. Since signals aren’t normally expected to change
simultaneously, the initial state is a good example of this:
POWER=0, FIRE=0, ARMED=0, LED=OFF, COUNT=N.
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 ‘FIRE’ causes a change in the ‘ARMED’ signal.
FIRE => ARMED=1.
To indicate that a change in one signal causes an immediate change in
another signal, list both signal changes in the same clock period:
POWER=1 => LED=GREEN.
For signal state changes with multiple dependencies, seperate the
dependencies with commas:
FIRE, ARMED => LED=RED.
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 ‘FIRE’ also causes ‘COUNT’ to
increment yields:
FIRE, ARMED => LED=RED;
FIRE => COUNT="N+1".
You can find this example and others along with their generated timing
diagrams on the homepage for drawtiming at
‘http://drawtiming.sourceforge.net’.
DIAGNOSTICS
Exit status is 0 on success, and 2 if the command fails.
COMPATIBILITY
The drawtiming command has been tested on FreeBSD, Linux, and Cygwin.
AUTHORS
This software package was written by Edward Counce
〈ecounce@users.sourceforge.net〉 Additional modifications by
Salvador E. Tropea 〈set@users.sourceforge.net〉
Daniel Beer
BUGS
None reported.