[PCB_FORUM] Re: Metric to English - English to Metric

  • From: "Patrick Jabbaz" <patrick.jabbaz@xxxxxxxxxx>
  • To: <icu-pcb-forum@xxxxxxxxxxxxx>
  • Date: Wed, 24 Aug 2005 14:58:15 -0700

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

Other related posts: