Ken:

I guess it takes someone who learned to drill on an old Excellon with ferrite core memory to
explain what these terms mean.  They are the CAM settings that a board house uses to view your
drill and router data.  The settings are indeed remnants from paper tape days.  In fact they come
from Numerically Controlled (not Computer Numerically Controlled) machine controllers.  They are
still applicable to today's drilling and routing machines.  It's that thing called backward
compatibility - kind of like the reason that Gerber format is still the default standard for
digital artwork file output.  They're both old and outmoded, but they work and everybody's
equipment can read it.

Anyway, on with the details:

1) Leading zeros means that all coordinates must be padded with leading zeros.  X1Y005 means that
your coordinate is X 10.0000 Y 00.5000.  In the original Tape format, there were no decimal
points.
2) 2.4 indicates the number format contains 2 digits to the left of the decimal and four digits
to the right of the decimal.  As mentioned in #1, there are no decimal points in the file.  They
are assumed based on the format and whether leading or trailing zeros are specified.  In the
above example, X1Y005 would be interpreted as X 0.0001 Y 0.0005 in a trailing zero format.
3) EOB LF/CR means that the End Of Block (read that as the end of a command) is terminated with
Line Feed and Carriage Return (ASCII 10 & 13) characters.  This is the same format that IBM
specified for the PC.  If you look at the code for an ASCII text file has it's hard return (enter
key) represented as Hex 0A0D.
4)ASCII refers to the code format as opposed to EIA.  EIA was easier for people to read on paper
tapes because the EOB character was the only one to use track 8 on the paper tape.  I believe
that EIA went the way of the Dodo once paper tape became obsolete.

This information is needed to load a drill or router file on a CAM system.  It should be supplied
with your data as it will eliminate trial and error when the drill and routing data is loaded
onto a CAM system.  With today's surface mount designs, my recommendation is that you always use
four decimal places in the Gerber files.  It won't hurt to specify them in the drill file
either.  Designs output using three decimal places can have pads move as much as 0.0005 inch
which can cause chip placement problems.

Don Vischulis

Ken Patel wrote:

> Our layout house deliverables state following line.
>
> "Drill file in ASCII format leading zeroes, format 2.4 EOB LF/CR " . I have
> couple of questions in that regards.
>
> (1)Can someone explain me what is "format leading zeroes, format 2.4 EOB LF/CR"?
>
> (2) After talking to my layout house, one of the comment I received was that
> instead of specifying leading zeroes, format 2.4 EOB LF/CR, it will be
> better to specify ___format in read me file - meaning layout house can use
> of their own e.g. 3 instead of 4.
>
> As I do not have expertise, I would like to get feed back from you before I
> change it.
>
> re,
> ken patel
> ______________________________________________________
> Ken Patel                       Phone:  (408) 490-6804
> 1708 McCarthy Blvd.             Fax:    (408) 490-6859
> Milpitas, CA 95035              Beeper: (888) 769-1808
>
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