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From:	"Edward Hennessy (ehennes AT sbcglobal DOT net)" <geda-user AT delorie DOT com>
Mime-Version:	1.0 (1.0)
Subject:	Re: [geda-user] Problem with BGA footprint generator
Message-Id:	<B9D4DA1C-55D8-4090-9428-84FF7C892753@sbcglobal.net>
Date:	Tue, 9 Jun 2015 14:29:16 -0700
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Jonatan,

In this device, the columns are letters and the rows are numbers (after rotating clockwise by 90 degrees, so that A1 is in the upper left).

http://cds.linear.com/docs/en/datasheet/4630fa.pdf

The datasheet also shows A1 in the lower left. I think the convention is to put A1 in the upper left on drawings.

Cheers,
Ed

Sent from my iPhone

> On Jun 9, 2015, at 1:47 PM, Jonatan Ã…kerlind <jonatan AT akerlind DOT nu> wrote:
> 
> Do you have examples of that inconsistency? Just checked with the JEDEC
> standard (see below) and also checked a datasheet from Xilinx and LT
> each, and they all agree. I checked these:
> 
> www.jedec.org/sites/default/files/docs/SPP-020A.pdf
> 
> http://www.linear.com/docs/46540
> 
> www.xilinx.com/support/documentation/package_specs/ft256.pdf
> 
> 
> There seems to have been some ambiguity with the JEDEC standard (JEP95
> SPP-010) regarding this numbering, which was clarified in JEP95
> SPP-020A.
> 
> The standard (SPP-020A) states that when viewing the package from top in
> the as-mounted orientation with A1 at the top left corner (i.e. same as
> looking at an unpopulated PCB footprint) the columns are enumerated
> 1,2,3 left-to-right and the rows are enumerated A,B,C top-to-bottom.
> 
> But to cite the background from SPP-020A:
> "The numbering practice for grid array packages has been clearly defined
> for square packages in JEP95,
> Section 3, SPP-010. The application of this practice to rectangular
> array packages is ambiguous and has led to inconsistency in the
> numbering shown in JEDEC outlines."
> 
> /Jonatan
> 
> On tis, 2015-06-09 at 13:21 -0700, Edward Hennessy
> (ehennes AT sbcglobal DOT net) wrote:
>> After looking around, I've found two different pin numbering schemes. (Could be more.)
>> 
>> When rotating the package so pin A1 is in the upper left, one scheme uses letters for the rows and numbers for the columns. The other uses numbers for the rows and letters for the columns.
>> 
>> Examining datasheets, Linear uses one scheme, and Xilinx uses another.
>> 
>> I need to update my footprint generator.
>> 
>> Cheers,
>> Ed
>> 
>> Sent from my iPhone
>> 
>>> On Jun 9, 2015, at 9:11 AM, DJ Delorie <dj AT delorie DOT com> wrote:
>>> 
>>> 
>>> I wonder if BGAs have the transistor problem... that the tool is
>>> correct for some BGAs and wrong for others, and if we fix it it will
>>> be correct for some BGAs and wrong for others.
> 
> -- 
> Jonatan Ã…kerlind
> +46702002897
> 
> 

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