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 separated by the following symbols:
- ,
- 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).
- ;
- The semicolon separator resets the list of dependencies
without incrementing the clock
- .
- The period separator resets the list of dependencies and
increments the clock.
- =>
- The "causes" separator renders dependency arrows
based on the current list of dependencies and then resets the dependency
list.
- -tD>
- The "delay" separator 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 separated
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, separate 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.
