see my earlier response on this

the via chekcbox takes precedence
which i think is logical since you are at the most
specific level

only by having this ability can you easily make exceptions to the design
rule

without a NO DRC i for one would hate to wade through 
a DRC about this exception, but i see your point
that there may be stuff going on without one's specific
awareness

i always thought that soldermask expansion 
belonged better as a property of the pad or via than as a design rule
but at this point,  whatever

re the default primitive settings as in this example

there is one more point that may need clarification and which
may be at the root of the original post

the 'default' setting applied in Tool Prefs Defaults
ONLY applies when using the Place Via command

if instead you are manually routing a board
and the * key when changing layers
then the via in the Via routing style is used
and it does not carry the tenting attribute
even if it matches the size & hole of the default via

Dennis Saputelli


Abd ulRahman Lomax wrote:
> 
> At 07:34 AM 3/4/2004, Leo Potjewijd wrote:
> 
> >>>I like my vias tented so I keep the tenting checkbox in the default via
> >>>settings dialog checked.
> >>>While interactively routing a PCB I noticed that the automatically
> >>>placed vias did not get tented (and the forementioned checkbox is still
> >>>checked)....
> 
> This discussion has gone back and forth a few times, yet some basic facts
> about the situation I found less than clear. There was an ambiguity about
> what was written. The "aforementioned checkbox" is the checkbox in the
> "default via settings dialog." That is a setting which will control the
> configuration of vias manually placed while that setting is active. It does
> not affect vias that are already placed, nor will it necessarily affect
> what the autorouter places. (You might expect it to, but Protel is put
> together from various programs that do not always function together with
> complete rationality. The 99SE autorouter, in particular, is its own
> creature and I'm not surprised to find that it does not respect in any way
> the "default" settings, just as the default settings may be altered
> whenever you edit a primitive as it is being placed. The default settings
> dialog is a convenience of occasional use, not an absolute control.
> 
> What I'm saying is that if the autorouter places vias which do not have the
> tenting checkbox checked, it is no big surprise once one is familiar with
> how 99SE works.
> 
> Historically, tenting was controlled only by design rule, the tenting
> attribute was one of the latest things added in the Protel 99 release, as I
> recall. It's a convenience. It's not particularly one that we requested,
> since using design rules to control tenting was already quite sufficient.
> 
> If there is a conflict between a design rule and the tenting checkbox, I'd
> place my bets on the design rule, given the history of the program. Which
> one is paramount? I don't know, and I'm not particularly motivated at the
> moment to go and test. I never check that tenting checkbox, precisely
> because I don't know the answer to the question. I do know that if the
> checkbox is unchecked and the design rule says "tent", it will be tented.
> That's enough for me.
> 
> Because the design rules are explicit and their scope can be readily
> determined (this gets even better in DXP), it is better design practice to
> control tenting through design rule than through a primitive attribute
> manually (or supposedly by default) assigned to each via. If somehow that
> checkbox got unchecked, how would you notice it?
> 
> Suppose you have vias of a certain size and you want to tent some and not
> others? The checkbox does make a way for you to do this, but there is a
> better way, and that is to convert the vias to pads, give the pads a
> distinctive name (say TENTED for the ones you want tented), and create a
> pad-scope design rule for Free-TENTED.
> 
> Vias are basically free pads with the restriction that they are only round
> and do not have names. If you want to distinguish some of these vias from
> others, it is better to select them and convert them to free pads (with
> Tools/Convert); then -- they will still be selected -- you can globally
> edit them to give them a distinguishing name.
> 
> >>>I do not want to end up with a board that has some vias tented and some
> >>>not, and the global edit on the complete board afterwards is too easiliy
> >>>forgotten.
> 
> Yes. Precisely. That's why the design rule approach is better.
> 
> >They (the autoplaced vias) did, too.... Seems the rule takes precedence
> >over the default setting.
> 
> The basic error here is in assuming that the default settings. I can easily
> understand why one would make the assumption. *The default settings are a
> convenience to speed up manual design, they don't control anything.*
> 
> What I don't know, it's an interesting question, is what happens if a
> design rule for tenting is in conflict with the checkbox on an individual
> via. I dislike ambiguities like that.
> 
> My preferred answer would be that the individual via's checkbox would
> override the design rule *if checked*, but that this would also create a
> DRC warning or error.
> 
> >Only when the mfg rule specifically targets vias it has any effect, a rule
> >specifying expansion for just surface and thru-hole pads does not change
> >the expansion for the vias....
> 
> As expected.
> 
> >The ASCII file states a neat "tenting=true" for the tented vias; for the
> >non-tented vias there is no such  statement..... I would expect
> >'tenting=false', but its completely missing....
> 
> As expected from the prior discussion. Certain fields are required in a
> primitive record, others are optional. The tenting field is optional. When
> Protel added new attributes, they did not require that all new attributes
> be made explicit. Good choice, I'd say.
> 
> >Further probing reveals no solutions but yet another mystery: the via
> >annular rings are calculated different from pad annular rings... I've seen
> >this one before, but still have no clues.
> 
> I don't think this is true, but it would not be entirely surprising. At one
> point there was an incorrect definition of annular ring in the annular ring
> manufacturing design rule dialog. That's been fixed, I think. For
> reference, "annular ring" refers to the difference between pad radius and
> hole radius. It is the width of the copper ring left if a hole as specified
> is drilled at the center of a pad as specified. Thus a 10-mil annular ring
> would be just barely sufficient to avoid hole break-out if the drill
> position wandered by 10 mils in any direction. Some Protel programmer at
> some point thought that it was the *diametric* difference, i.e., twice the
> radial difference.
> 
> >To top it all off: I'm running a fresh P99SE/sp6 installation on a brand
> >new computer under a fresh installed W2kPro/sp4, all files on local disk.....
> >
> >I just about had it with P99SE.
> 
> Nothing has been reported in this thread that represents a malfunction of
> the program, per se, only an incorrect (albeit understandable) expectation
> -- the usual cause of serious 99SE frustration.
> 
> The 99SE autorouter apparently does not set the via attributes according to
> the default via settings. This is not a bug, in fact. If you have a default
> via of, say 40 mils with a 20 mil hole, and you have vias set up for the
> autorouter of 30 mils with a 15 mil hole, the autorouter will follow the
> autorouter settings. And that dialog does not have any provision for
> setting a tenting attribute.
> 
> The default settings are *only* intended to guide manually placed
> primitives. The default settings have no effect on any autorouter-placed
> primitive, if I am correct. This is not unique to vias.
> 
> If I've misread or misunderstood something and there is a bug, I'd be happy
> to look again!

-- 
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