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INTRODUCTION
Bad Film - Again
Today's PCB CAD systems are rapidly growing in power and
sophistication. Unfortunately, that power often does not apply
to the next step in the PCB fabrication process: photoplot data.
Any PCB designer will happily relate horror stories involving
expensive and time-consuming mistakes made at the photoplot
service bureau due to misunderstandings involving the photoplot
data.
These misunderstandings occur for several reasons. For one, many
CAD users don't really understand the photoplotting environment,
so they can't really check the data before sending it out to be
plotted. For another, the data is by its very nature incomplete
and requires more information to be sent along with it (the
"Aperture List"). This information can easily be lost or
mistranscribed by the photoplot vendor. Further, the data itself
is often in a nonstandard format, or even wrong - a surprising
number of high-quality PCB CAD packages have photoplotter output
troubles.
GC-PREVUE addresses these problems by looking at your CAD output
just like a photoplotter does, then allowing you to inspect it in
a WYSIWYG fashion on your PC's graphics screen. As you use GC-
PREVUE, you will come to better understand the photoplotting
process and will be better able to avoid plotting problems,
thereby saving time, money and hassles.
If your job looks good on the GC-PREVUE screen, you're on the
way to getting good film.
GC-PREVUE can produce checkplots on PostScript and HPGL
devices, which you can FAX to the photoplot vendor.
GC-PREVUE can create a single file completely describing your
job. This file can be read by the photoplot vendor with
another copy of GC-PREVUE, or any other GraphiCode software
including GC-PREDITOR, GC-CAM and OEM versions of GC-CAM.
This document explains how to use GC-PREVUE, and assumes that you
know a little about Gerber photoplotter data. If you need
information on basic photoplotting principles, please read the
GERBER.DOC file before beginning.
PREVUE Tutorial
This tutorial will provide the necessary procedures to generate
sample data for a board house. It is assumed that you have never
used GC-PREVUE before. The following steps will help you learn
many functions of GC-PREVUE as well as provide a process that
will insure data integrity.
For this tutorial, demonstration files will be used. They
include: DEMODAT1.GBR and DEMODAT2.GBR which are CAD generated
GERBER files; DEMODAT3.NC which is a NC drill file; the aperture
list DEMO.APR; and the drill rack DEMO.RCK.
Note: If you are running the automated tutorial demonstration,
TUTORIAL.BAT, you need only follow along with the documentation
and strike the <SPACE BAR> key when prompted by the program. Do
not attempt to input values from the tutorial or other
keystrokes, as it will create a confusing demonstration for you.
Note: All keystrokes will be indicated with the words "Type" or
"Press". "Type" indicates the following text in quotes must be
entered (but don't actually type the quotation marks). "Press"
indicates that a key or combination of keys needs to be pressed.
Starting GC-PREVUE
Once you have installed GC-PREVUE by running the MAKEPVU program:
Type: "GCPREVUE".
Press: Enter.
The main GC-PREVUE screen will appear, with the cursor located in
the Main Menu at "Layers". From top to bottom, notice: the Main
Menu, the Help line, Layer list area, Aperture Lists area, and
Configuration File area, which shows the current Drill Rack, Bed
size and graphics card type. These areas define the complete
working environment, including CAD data files, apertures, drills,
and system parameters.
In the Main Menu you will see the: Configuration, Layers,
Apertures, and Drills fields. These are used to move the cursor
to modify the areas mentioned above.
Getting Started
For the purposes of this tutorial, we need to load a special
configuration file.
Press: "C" to select Configure on the main menu.
Press: "L" to Load a configuration.
Type: "TUTORIAL" to specify our tutorial configuration.
Press: Enter to load.
Loading CAD Gerber Files
Loading CAD files is performed in the layer list. To move the
cursor into the Layer List:
Press: L, or select Layers in the Main menu with the mouse
(ClickLeft on "Layers").
The cursor will jump into the layer list, under the filename
column. This field is where CAD data filenames will be entered
for loading. Also, notice that the Layer List contains many
different colored rows called "layers". GC-PREVUE keeps each
loaded file on a separate a layer, and lets you tag each layer
with one of 12 colors.
To load the demo CAD files:
Press: F10 to invoke the directory feature. The directory
feature lists a directory of specified files.
Type: "*.gbr" in the directory window.
Press: Enter. A list of .GBR files will appear.
Move: the cursor to DEMODAT1.GBR.
Press: Spacebar to select the file.
Move: the cursor to DEMODAT2.GBR.
Press: Spacebar to select this file also.
Press: Enter. Notice that the names of the files you selected
are now on layers 1 and 2.
Now that the filenames have been selected, we must load them.
Press: CTRL M (or Click the middle mouse button) to bring up
the Layer list menu.
Functions may be selected from the menu by the mouse or by using
single-key equivalents. Single key equivalents are designated in
yellow next to the function name in the menu. Quick-keys will be
used in this tutorial to invoke functions. Keep in mind that
anytime you are not sure which features are available, Press
CTRL-M. You can also pop up a menu using the mouse, using
ClickCenter (or ClickBoth for two-button mice).
Press: F1. This will start the loading procedure.
A window will appear that asks for the data type.
Press: "G" to select Gerber.
The next window that appears contains fields which determine the
CAD data format.
In the Layers field:
Type: "all". This will load all both our data files.
Press: down arrow twice to move to the Plotter field.
The Plotter field provides for easy save and restore of the
various format settings specified in the remaining fields of this
window. Since these fields (precision, zero suppression etc)
don't change very often, you can save their settings to a file
using the .PDF filename extension.
Type: "GERBER.PDF".
Press: down arrow.
Notice how some of the below fields have changed to take on the
parameters previously saved in GERBER.PDF.
If the PDF doesn't have the correct settings, you can edit the
fields to appropriate values. For this demonstration, all values
in GERBER.PDF have been set properly.
Press: Enter.
Before DEMODAT1.GBR and DEMODAT2.GBR are loaded, GC-PREVUE will
issue an error message saying that "Aperture list A is not
loaded" and will prompt "Do you want to generate it from the
input data?
Press: Enter or "Y" to indicate "yes".
GC-PREVUE will build an uninitialized aperture list which
corresponds to the CAD Gerber data. As the aperture list is
being created, a red scroll window will appear, indicating D
codes that are missing from the aperture list. Do not be alarmed
about these messages, this data is informational in this case,
and does not mean that there is a problem.
Once the loading is complete, a message will appear stating:
"> Press any key to continue <".
Press: Spacebar or any key on keyboard.
Notice the Aperture List area. You now have an UNTITLED aperture
list loaded in position A.
Editing the aperture list.
Both DEMODAT1.GBR and DEMODAT2.GBR layers are loaded, but the
data will not have any size or shape to it, because the aperture
list needs to be initialized.
Press: left arrow key to move onto the "Aps" column of the
layer list.
Press: F10 to pop up and edit the aperture list.
The aperture list will appear with multiple fields that are
uninitialized. The cursor is located under the Code column. To
illustrate how editing can be accomplished:
Move: the cursor to the "Drl" column.
The "Drl" column provides referencing of apertures to Drills.
The number specified indicates the drill position on the tool
rack. (The tool rack will be discussed in later sections).
Type: "1". Now this aperture will use tool 1 as its drill.
Move: the cursor to the R90 column.
The R90 column specifies which aperture will be used to replace
this aperture when it is rotated 90 degrees. Therefore, if you
have a .1 X .05 rectangle, and you wish to rotate the data, you
would define a .05 X .1 rectangle and use its position as the R90
value.
Type: "2".
Now, aperture 1 will be replaced with aperture 2 when rotated 90
degrees.
Move to the Code column. This column indicates the Gerber D code
associated with this aperture. You do not want to change this
column.
Move: to the Type column.
Notice the yellow window below the aperture list window. You
will see a list of aperture shapes supported by GC-PREVUE.
Press: SHIFT F5. Notice how the Type has changed to Rectangle,
and that the dimensions column has two parameters.
Move: to the first dimension.
Type: "0.1".
Move: to the second dimension.
Type: "0.05".
You have just setup the first aperture to be a .1 inch by .05
inch rectangle. The rest of the aperture list can be defined in
the same manner. For this demo, you are not required to
initialize the entire list, because one has been setup for you.
To load the provided aperture list:
Press: Esc to get out of the aperture list editor.
Press: Esc again to return to the Main Menu.
Press: "A" to go to the Aperture list setup area.
To save the work you've done on this untitled aperture list:
Press: F4 to write to disk.
Type: "DEMOTEST.APR" to indicate the aperture list filename.
Press: Enter.
The provided aperture list is called DEMO.APR. To load DEMO.APR:
Press: Ctrl F1 to unload DEMOTEST.APR.
Type: "DEMO.APR"
Press: F1. The aperture list DEMO.APR is now loaded.
To inspect the aperture list without editing:
Press: F3.
You will see the aperture list appear with all fields set to the
correct values.
Once, you are done inspecting the aperture list:
Press: Esc to get out of the aperture list viewer.
Press: Esc to go back to the Main Menu.
Loading CAD Drill files
Loading Drill files is very similar to loading Gerber files. The
basic difference is the data type you are loading. From the main
menu:
Type: "L" or select Layers to move into the layer list.
Press: the down and right arrows to move to the filename column
on layer 3.
Type: "DEMODAT3.NC"
Before loading the drill data, the layer must be declared as
using the tool rack instead of an aperture list.
Press: the left arrow to move to the Aps column.
Type: "T". Now, the layer is associated with the tool rack.
Press: F1. This will start the loading procedure.
A window will appear that asks for the data type.
Press: "D" to select Drill.
The next window that appears contains fields which determine the
Drill data format.
In the layers field:
Type: "3". This will load only layer 3.
Press: down arrow twice to move to the Plotter field.
Type: "NCDRILL.PDF".
Press: the down arrow. Notice how some of the below fields
have changed to take on the parameters of NCDRILL.PDF.
If the PDF doesn't have the correct settings, you can edit the
fields to appropriate values. In this case all the values are
correct.
Press: Enter.
Before DEMODAT3.NC is loaded, GC-PREVUE will issue an error
message saying that "No drill Rack loaded" and will prompt "Do
you want to generate it from the input data?
Press: Enter or "Y" to indicate "yes".
GC-PREVUE will now build an uninitialized tool rack which
corresponds to the drill data. As the drill rack is being
created, a red scroll window will appear, indicating T codes that
are missing from the Tool Rack. Again, do not be concerned about
these messages, this data is informational in this case, and does
not mean that there is a problem.
When loading is complete, a message will appear stating "> Press
any key to continue <".
Press: Spacebar or any key on keyboard.
Notice the Drill Rack entry at the bottom of the screen. You now
have an UNTITLED tool rack loaded.
DEMODAT3.NC is loaded, but the drill data doesn't have a set size
to it until the Drill rack is initialized.
Editing the Drill Rack
The Drill rack is a list which defines tools used by the drill
data. With each tool is associated a diameter. To edit the
drill rack, you could move the cursor to the Aps column again and
press F10, but instead we will:
Press: Esc to move back to the Main Menu.
Type: "D" or select Drills. The cursor will jump into the
Drill Rack menu.
Type: "E" to edit the Drill rack.
The Drill rack will appear with multiple fields that are
uninitialized. The cursor is located under the diameter column.
To illustrate how editing can be accomplished:
Type: "0.05" which defines a 50 mil tool.
Press: down arrow to move to the next tool position.
For this demo, you are not required to initialize the entire
drill rack since one has been set up for you. When you feel you
understand how to edit the drill rack, save the work you've done
by:
Press: Esc to move back to the drill menu.
Type: "S" to select Save. The save drill rack window will
appear, prompting for the drill rack filename.
Type: "DEMOTEST.RCK".
Press: Enter.
The provided aperture list is called DEMO.APR. To load DEMO.APR:
Type: "L" to select the Load function.
Type: "DEMO"
Press: Enter. DEMO.RCK will now be loaded.
The loaded tool rack will appear with its values initialized.
Once, you are done inspecting the drills:
Press: Esc twice to go back to the Main Menu.
Verifying That the Data is Correct
Now that all the CAD data is loaded, the data must be verified.
This can be done by using GC-PREVUE's graphical editor, where the
data can be viewed as true WYSIWYG. The Report and CheckPlot
features in the Layer list add further checks.
Type: "L" to select Layers in the Main Menu.
The Report Function
Report tells the extents of the layer, the aperture list used,
how many of each aperture are used as pads or traces, and the
total number of pads and traces. To invoke Report:
Press: F3.
The report window will appear. The report will be the first
indicator whether your data is correct. Compare the Report
information with that from the CAD package. If the dimensions
are wrong, check the precision and zero suppression used when
loading the data. If they seem correct, you may need to output
the CAD data again. If the number of pads and traces do not
match up, output the CAD data again. If the report data matches
the CAD data specifications, then the data is ready to be viewed
for checking.
The Graphical Editor
The graphical editor is accessed through the layer list. To move
into the graphical editor:
Press: F2
Notice that the screen is now in graphics mode, and the data you
have loaded is drawn on the screen. The next move is to window a
small area and zoom up on it so that it can be seen with much
greater detail. To window data:
The graphical editor contains several distinct areas: the main
viewer window (the big part); the coordinate system window (the
upper right part); the setup status window (the lower right
part); and the ever-present Help line (the top part). Pressing
Ctrl-M or clicking the center mouse button pops up a menu from
which functions can be selected. The viewing window represents
data in true WYSIWYG form. The coordinate system window displays
three different coordinates: User, Absolute, and Relative, plus
it displays the step grid and snap grid values. The setup status
window indicates each layer's aperture list and view/hide mode.
Just looking at your data is an excellent quality control step.
Humans are exceptional at recognizing details of shapes and
patterns. Subtle data errors can be found by scanning the data.
To zoom in on a section of data:
Move: the cursor to the lower left hand corner of the data,
either with the mouse or the arrow keys.
If you have a mouse:
Drag (press and hold down) the left button on the mouse, move
the cursor to the other corner of the zoom area, then let up on
the mouse.
Now Click the left key to execute the zoom in feature.
If you don't have a mouse:
Press: Ctrl W.
Move: the cursor to the opposite corner of the zoom area.
Press: Ctrl W again.
Type : "+" to zoom up on the data.
What you may have already noticed is that the drill data is
obscured. This is due to the fact that data is drawn from the
bottom layer up, and the drill layer is below the Gerber layers.
Thus the drills are over-written by the pads. This can be
remedied however, by moving the drill layer to the top.
Type: "S" to move the cursor into the Setup Status window.
Move: the cursor to layer 3.
Press: F8. Notice that the old layer 3 is now layer 1.
Press: Esc to move back to the viewing window.
The drill data should appear, with the pad data below.
Sometimes the data can become hard to view when several layers
are drawn. GC-PREVUE will allow individual layers to be hidden.
Press: "S" to move into the Setup Status window.
Move: the cursor to layer 3, where the "V" resides.
Press: Spacebar to toggle the "V" (view) to "h" (hide).
Press: Esc to move back to the viewing screen.
Now, you can scan through the data to look for possible errors.
To scan through the rest of the data, the panning feature can be
used. Pan shifts the viewer window from the start point of pan
to the end point of pan.
If you have a mouse:
Move the cursor to the top of the screen. Drag (press down and
hold) on the center button while you move the cursor to the
bottom of the screen. Release the button. (For two-button
mice, drag on both buttons at once.)
If you don't have a mouse:
Move: the cursor to the top of the screen.
Press: "P".
Move: the cursor to the bottom of the screen.
Press: "P". What you see on screen is new data.
Continue to use the Pan feature until all the data is viewed.
When all of layer 2 is verified, hide layer 2, set layer 3 to
View, and pan through its data.
As you scan though the data, look for problems such as
unterminated traces, insufficient gaps between entities, mis-
registered layers, and annular ring errors.
If data seems to be incorrect, check the following:
The data may have been loaded improperly. The CAD package output
the data incorrectly, or the design is wrong. To verify if the
data is loaded improperly, ask yourself:
Is data absolute or incremental?
Was the whole digits or precision set improperly?;
Was the zero suppression leading, trailing or none?
Did I specify the wrong data type?
If you are sure you have specified the correct format, the data
from the CAD package could possibly be the culprit. Output the
CAD data again, and reload. If the data is still wrong, then you
probably have a design flaw.
Using Checkplot
CheckPlot will allow you to create a Postscript or HPGL file of
your data. You can then send the files to a postscript printer
or penplotter to get a hard copy of the design. From the copy,
design flaws may be determined. To use Checkplot:
Press: ESC twice to go back to the Layer list.
Move: the cursor to layer 2, which is the top Gerber layer.
Press: F4 to invoke Checkplot.
The Checkplot window will appear with option fields that allow
you to modify the output.
Type: "DEMOTEST.PLT" in the Output file field.
This will be the file saved to disk. If you have a postscript
printer you could type "PRN" to plot directly to the printer. If
the printer you have is not a postscript printer, the file must
be written to disk and Postscript interpreter software such as
GoScript will need to be used to generate a bit-mapped copy of
the postscript data. For demo purposes, let's write the file to
disk.
Move: to the Layers field.
Type: "2".
Move: to the Plotter field.
Press: F10. GC-PREVUE will bring up a directory of supported
output devices.
Select: Postscript.
You may wish to select one of the penplotters from this list
instead, depending on your application.
Move: to the Style field.
Press: Spacebar.
Notice how the options are toggled through. The options
available to you are Normal, Transparent, and Ball and Stick.
Normal means that the data will appear as you saw it in the
Graphical Viewer. Transparent mode, creates an outline of the
data. And Ball and Stick gives center line information of traces
and outlines of pads.
Press: Spacebar until "Normal" appears.
The other available features are set to the correct values. To
find out about these features, you can access the information
from the manual.
Press: ENTER.
The data will output a Postscript file to disk.
Creating a Job (PWK) File for the Photoplot Vendor
When the data is verified to be correct, it is time to create a
PWK file to send to the photoplot vendor. This file will contain
all loaded CAD data, aperture lists, drill rack, and
configuration information. You will no longer need to relay to
the vendor the format of the data. To create the PWK file, from
the layer list:
Press: F6, which is the Save All function.
A window will appear that asks for the filename to save to.
Type: "DEMO"
Press: ENTER. Notice that GC-PREVUE adds the default extension
to the filename.
Remember that the single file feature is most useful if your
photoplot vendor has GraphiCode's GC-Preditor or GC-CAM (or OEM
equivalent) packages. Otherwise, along with the PWK file you
will need to send all the other files, including the aperture
list, drill information, and data formats (your photoplot vendor
can use his copy of GC-PREVUE to make sure the other files make
sense). Either way, GC-PREVUE should go a long way to reducing
the possibilities of errors.
Loading and Viewing a Single PWK File
To demonstrate the capability of single file loading, we need to
first exit the GCPREVUE program.
Press: ESC
You are now back to the Main Menu bar. You will now want to
"Exit" the program.
Type: "E"
The program will now go through a series of prompts. The first
prompt will ask "Do you really want to quit GC-PREVUE?"
Type: "Y"
The next prompt will ask "The system configuration has changed.
Do you want to save it?:"
Type: "N" to avoid overwriting the TUTORIAL configuration file.
We are now back at the DOS level. Again, start the program.
Type: "GCPREVUE"
Press: ENTER
We are now back into the GC-PREVUE program. To reload the work
you just saved, complete the following sequence of keystrokes.
Type: "L"
We have now entered the Layers List
Press: F7
This keystroke will bring up a window stating: "Read saved work
from file:"
Type: "DEMO"
Press: ENTER
You will now see DEMODAT3.NC, DEMODAT1.GBR, and DEMODAT2.GBR in
the Layer list, and the files will be loaded. Additionally,
DEMO.APR and DEMO.RCK will now be load in the Aperture List area
and the Drill Rack.
We will now enter the Graphical Viewer to inspect the data.
Press: F2
You can now see all three data files displayed, in the same
viewing order in which we saved them with the F6 command earlier.
Imagine that you are the photoplotter operator receiving the data
- you know EXACTLY what the designer had in mind!
In this tutorial we covered the basics of plot data loading,
aperture list & drill rack creation and editing, as well as
graphical viewing and zooming.
GC-PREVUE has many functions and capabilities not covered in this
tutorial. We encourage you to read the manual, and try loading
your own data and become more comfortable with GC-PREVUE.
Remember that GC-PREVUE is shareware, so we encourage you to
share it with your friends and colleagues in MAKEPVU.EXE form.