[PCB_FORUM] Re: Valor and Metric

Dharma:
 
I previewed this thread briefly to see that you needed to convert units within 
Allegro. Yes, it is observed that there is an ongoing rounding issue with 
Cadence Allegro. I am not crystal clear as to what happens if you once again 
revert back to the original units setting; ie. creep effect or not.  But I 
think I saw one comment from Carl Mussetti that it is not a good practice to 
switch design units if you can help it.  The rest of the posts I  needed to 
delete....
 
Anyway... Valor and you units conversion.    There is also a setting in the 
Valor tool that controls the units.  When you are loading data into Valor are 
both CAD/CAM tools synchronized to the same units? Also when you generate your 
post process data: artwork, NC Drill and NC-Mill, etc.  are these parameters 
also consistent?  If not, try doing everything consistently and see if that 
resolves the NC drill data issue. (I am not sure how the ERF data may be 
effected when you are using Valor)
 
Sincerely yours, 

Michael Baumstark 

Staff PCB Designer - BSEE, CID+ 
Motorola - Advanced Product Technology Center 


-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Dharma Kemp-Bresett
Sent: Wednesday, August 31, 2005 9:14 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Valor and Metric


Hi All,
I have a new metric question for you. I need to look at a metric design in 
Valor but every time I do I get a "scaling" of the drill. I am outputting all 
of my artworks, drills, and such in metric and all with the same parameters. 
However when I load them into valor the drill is "scaled" compared to the rest 
of the artworks. Is there a checkbox or something that I am missing?
Thank you in advance,
 Dharma

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Andrew Noonan 
(annoonan)
Sent: Thursday, August 25, 2005 11:56 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Metric to English - English to Metric


Hi Kanak,
Someone made an interesting suggestion yesterday. When you must switch back and 
forth, set the accuracy in millimeters to 4 decimal places, and the mils to 2 
decimal places. Apparently this removes the rounding errors. I haven't tried it 
my self, but it's worth a try if you need to use this approach.
Andrew

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Kanakaraj
Sent: Wednesday, August 24, 2005 9:11 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Metric to English - English to Metric


Hi,
 
In my project, the customer has given the mechanical dimensions of the 
connectors and mouting holes in mm. ( with three digit accuracy like 21.213 
mm). I place the connector with milimeter as measurement unit and switch back 
to mils for routing.
 
When we are doing the dimensioning, we again switch back to milimeter, then we 
encounter errors upto two decimal points. ( the connector fixed at 21.213mm is 
showing as 21.192 mm.. for an example).
 
have any one encountered issues like this? how can this be fixed.
 
Regards
~Kanak
 

----- Original Message ----- 
From: george.h.patrick@xxxxxxxxxxxxxx <mailto:george.h.patrick@xxxxxxxxxxxxxx>  
To: icu-pcb-forum@xxxxxxxxxxxxx <mailto:icu-pcb-forum@xxxxxxxxxxxxx>  
Sent: Thursday, August 25, 2005 3:39 AM
Subject: [PCB_FORUM] Re: Metric to English - English to Metric

 
The question remains:
 

WHY switch back and forth?

 
If the board is started in one unit, you are making it harder on yourself and 
others switching back and forth, even with NO round off errors.  The grids are 
different, the trace widths are different (unless you LIKE typing two decimal 
places all the time).  It is senseless to be switching it around, unless it is 
just to make extra work for yourself or your international partner.  Why not 
just KEEP IT SIMPLE (K.I.S.S.) :)
 
-- 
George Patrick
Tektronix, Inc.
Central Engineering, PCB Design Group
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
Phone: 503-627-5272         Fax: 503-627-5587 <http://www.tektronix.com/> 
http://www.tektronix.com     <http://www.pcb-designer.com/> 
http://www.pcb-designer.com

It's my opinion, not Tektronix' 

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Patrick Jabbaz
Sent: Wednesday, August 24, 2005 14:58
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Metric to English - English to Metric



Here is the trick to make it work, In Allegro,

You can switch units from metric to mils, and vise versa without errors, if you 
have the following setup:

User Units mils use 2 decimal places 

User Units  millimeter  use 4 decimal places

Using this process, allows you to switch back and forth without any round off 
errors.

Patrick Jabbaz

Sr. PCB Design Eng.

Xilinx

2100 Logic Drive

San Jose, Ca 95124

Direct: 408-879-4709

M: 408-621-6533

email: patrick.jabbaz@xxxxxxxxxx

 


  _____  


From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Wednesday, August 24, 2005 2:26 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Metric to English - English to Metric

 

Hi Richard,

 

Perhaps more than a decade ago, the CPU and code speed may have been an issue.  
But, in the realm we are talking about (a printed circuit board and the range 
of numbers and precision necessary) IMO and IME the compiler imposes no 
significant restrictions, nor does the "math processor" in the CPU.  Again, it 
is simply a matter of knowing where the decimal point is.

 

In Allegro, you don't convert because the tool can not handle it.  In a tool 
that can adequately handle it, this is not an issue.

 

Regards,

 

Austin 

 

 -----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of richard moffat
Sent: Wednesday, August 24, 2005 5:15 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Metric to English - English to Metric

Cadence is probably making a compromise for speed.  The way that other tools 
may allow a seemless interchange is to have a greater length of significant 
numbers in the internal database, especially converting metric->imperial.

 

The programmers are restricted to that they are given:  The C compiler, and the 
maths processor on the CPU.

 

In short:  don't convert!


>>> austin@xxxxxxxxxxxx 25/08/2005 9:08:15 a.m. >>>

Hi,

> Conversely, 1/10 (0.1) cannot be exactly represented in base 2...

I design ASICs, and I have done a LOT of arithmetic functions in ASICs, and
use decimal points all the time.  All hardware arithmetic functions are done
in base 2.  It's simply a matter of knowing where the decimal point is and
using enough digits.  Yet, it goes on to explain the solution (as I said,
knowing where the decimal point is)...so I fail to see the *real* problem.

As was pointed out, PADS has no problem switching back and forth between the
two unit systems, so I simply don't believe Allegro can't do it as well.  It
seems like this may be a self imposed restriction:

> The real issue is that some numbers can't be represented exactly in the
> standard floating point representation.

Why do they have to use "standard" floating point representation anyway?
Sounds like someone programmed themselves into a corner, and instead fixing
it, they are trying to come up with explanations...instead of solutions.
Sigh.  To me, this is a huge weakness of Allegro.

Regards,

Austin



  _____  





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