On Fri, 23 Feb 2001 13:48:18 -0800, you wrote:

>       One rule that I follow across all my experience is that there must
>only be one company reference library. Every designer must have access to
>the reference library and use the reference parts. Even if there is a one of
>prototype there should not be any symbol or footprint which is not
>accessible to all designers and has not been designed to meet company
>requirements. Anything short of this overall governing rule is a one way
>road to disaster, or at least a few tears, gripes and complaints, throwing
>money away, finger pointing and lost productivity.

Sounds great and how can any engineer regardless of "diversity of
cultures" complain about finding all parts in one library ready checked and
approved? 


Let me tell you my experience as a contract (circuit/software) design
engineer in a company that took your rule a little further. 

Working on a large project (and I mean large) some young aspiring engineer
come up with statistics showing that each different component used in the
project was going to cost the company around L20,000 in overheads
associated with buying stocking and maintaining spares. Compared to a
previous project if engineers just used a little more commonality the
company would save millions. 

That engineer was appointed the project component authority and a project
part database and CAD libraries were set up. 

To use a component in your design which was not already in the approved
database required you to fill out a request form with written justification
of your need to use that component and proof that no other existing
component could be substituted. The request was passed on to the project
component engineer who checked and reported on availability and obtained
data sheets for the project library. The request was then passed on to the
component authority who had to approve the request. This often resulted in
a simple NO and you try again or eventually have  a meeting where you had
to verbally argue your request and were sometimes asked to go talk to other
project engineers to see if an approved component they were using could be
replaced by something else which both of you could use. Approved components
then got passed on to the CAD library manager to be added to his list
awaiting symbol and footprint creation. I don't think this process ever
happened in less than a week and if anyone in the chain was sick or on
holiday or off site the process stalled till they got back. 

The component authority maintained an overall project component type count
which was obviously calibrated in management brownie points he would get
for saving the company all this notional money. 

I remember once we failed to justify a cheap 8 bit CMOS ADC with 4 channel
mux which needed to have about +4v full scale. We were told to design in a
vastly over specified 4 channel 12 bit flash ADC with built in references
for +/-10v full scale. We didn't notice at the time (because we never
considered that part to be an option) but it required a split power supply
and we had to add a dc-dc convertor to the design just for its negative
rail. 

Anyhow...

The CAD system scripts were set up which only allowed components from the
approved library for netlist, partlist generation and as a consequence even
design rule checking. That meant if we wanted to capture the design before
all components had been approved (like always) we had use components from
unapproved libraries just to get a schematic print and could not DRC or
partlist it. We had to make and use unapproved symbols and hope the library
manager was going to make a compatible symbol when it was approved. I'm
sure different engineers ended up making different symbols for the same as
yet unapproved parts. We also had the pain of constant updating as part
became approved. 

The company also had requirements for formal and peer review of designs
which is kind of impossible when you don't have an accurate schematic and
partlist to be reviewed. The reviews could obviously result in changes, you
might have gone through all that crap for a part that got deleted, and may
have to go through it all again for any additions. 

Overall it pissed off every design engineer, it may have saved some
overheads, it certainly extended the development time, to some extent hurt
design performance, reliability and production costs. 

The "one approved CAD library" was one of the most painful tools used to
enforce this policy. 

I don't disagree with your rule, just wanted to make people aware of the
horrible slippy road I have been on and down which your rule could be the
first step. 

Cheers, Terry.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*  This message sent by: PROTEL EDA USERS MAILING LIST
*
*  Use the "reply" command in your email program to
*  respond to this message.
*
*  To unsubscribe from this mailing list use the form at
*  the Association web site. You will need to give the same
*  email address you originally used to subscribe (do not
*  give an alias unless it was used to subscribe).
*
*  Visit http://www.techservinc.com/protelusers/subscrib.html
*  to unsubscribe or to subscribe a new email address.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

________________________________________________________

To leave the EDAFORUM discussion list, send a email with
'leave edaforum' in the body to '[EMAIL PROTECTED]'

More Information : http://www.dolist.net

Reply via email to