timepic(1) — the Plan 9 manual

TIMEPIC(1)TIMEPIC(1)

NAME

timepic – troff preprocessor for drawing timing diagrams

SYNOPSIS

timepic [ files ]

DESCRIPTION

Timepic is a pic(1) and troff(1) preprocessor for drawing timing diagrams. Timepic code is contained between .TPS and .TPE lines:

 .TPS width row-height
statement-list
 .TPE

There are two types of timepic statements: variable definitions and signal definitions. Variables are defined with the syntax

var = expr;

where expr is an arithmetic expression involving floating-point constants and previously defined variables. Currently only basic arithmetic (+, -, * and /) is supported. Signals are defined with the syntax

name events ;

where name is a name that must be quoted unless it’s a valid symbol. Events is a list consisting of the following things:

•

The current time can be set using an arithmetic expression, that may be followed by a symbol interpreted as a unit. For instance if you defined μs = 1000; then 1μs and (x+2)*3μs are both valid time expressions. Note that x+2μs is interpreted as (x+2)μs which may or may not be intended behaviour.

A time expression can be preceded by + to mark it as relative to the previous time. The first time is zero.

A time expression can be followed by a symbol name in square brackets. The symbol is then defined with the time.

•

An expression of the form :name creates an ‘event’ at the current time, changing the value of the signal to name. name can be a symbol (which is not evaluated), a numerical constant or a string in single quotes. The values 0, 1, x and z have special meaning, unless they are quoted.

•

A pipe symbol | draws a vertical dashed line at the next event.

•

An expression of the form expr{events} evaluates the expression, rounded to the nearest integer, and then repeats the events the specified number of times. It is illegal if the expression evaluates to a negative number. It is also illegal to use absolute times in the events list. It is however legal to nest this construct.

EXAMPLES

 .TPS 6 0.4
c=5;
clk +5{:1 +.5c:0 +.5c};
data :x 2.3c:DQ 4c|:x;
valid :0 2.3c:1 4c:0;
ready :0 3.6c:1 4c:0;
 .TPE

FILES

/sys/src/cmd/timepic.c

BUGS

Yes.