Good morning Michael, etc.
FLASH is a term that comes from the Gerber language, which was developed for
the Gerber photoplotters at a time when memory was expensive. The Gerber
language is very simple and results in extremely compact data files,
especially (or only) when you are using FLASHes.
A photoplotter uses a wheel of images, a shutter and a lamp. The images on
the wheel represent the D-codes (shape and size) which can be projected on
the film when the shutter is opened. When using FLASH the shutter is opened
and closed projecting a single D-code on the film, resulting in an exact
replica of it . When using TRACE (or DRAW) the shutter is opened and the
film is moved from the desired starting position (X1,Y1) to the desired
ending position (X2,Y2). The result is a line on the film with the width of
the D-code. Typically you would use a circle for this operation and
theoretically other D-codes can be used also, but it is not a good idea to
draw a "snaking" line with a square aperture as the line thickness will not
be constant..
In today's photoplotters lasers are used to expose the film and the
operation is quite different, but the software to drive the laser still
behaves and accepts input like the old photoplotters.
When making a circuit boards you obviously need to use TRACE (or DRAW) a lot
to represent the copper traces and you can use FLASH for the many different
parts of the component footprints.
When making stencils you can use to FLASHes a lot and need TRACE only for
things like board outlines, text and a few others. However some circuit
board design programs or designers seem to like TRACE and build up D-codes
from many TRACEs using various D-codes, rather than defining them as single
shapes. The result is a very large data file and potentially some other
"little" headaches.
The "Standard" shapes for D-codes are: Circle, Oblong, Square and Rectangle.
Other shapes can be produced using a macro, which uses standard shapes to
build up a special shape.
Normally a Gerber file consist of a Data File plus an Aperture List (Gerber
274D) or a Data File with the aperture information included (274X). The
aperture list is not standardized, so you will always need the list that was
generated when the data file was generated.
To get a good description of the Gerber format check the out the following
location: http://www.barco.be/ets/data/rs274xc.pdf
Regards, Ahne Oosterhof
A-Laser, Inc
503-641-9428
-----Original Message-----
From:
Sent: Wednesday, July 19, 2000 04:29
Subject: [TN] Flash
Hi
Excuse the newbie question, but what exactly is FLASH in the sense of d-code
type? I've checked the archives but can't find the answer. It appears to be
in
contrast to TRACE. Someone suggested that the latter is an outline, and
FLASH is
a solid (filled-in) shape. Is that right?
Is there a standard list of shapes and sizes for TRACE and FLASH? I.e. if I
run
across a d-code which I don't know (listed as FLASH), how do I find out what
shape it is?
Actually, that's several questions. Sorry. Thanks IA.
Michael Fennema,
Uni-Circuit Inc.
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