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Magic Mailing List |
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From: Steven M Brown (smbrown AT cse DOT psu.edu) Date: Wed Oct 22 2003 - 17:54:26 EDT
On Wed, 22 Oct 2003, R. Timothy Edwards wrote: > > Idle thoughts on how to accomplish this without breaking the technology > > file, the ext file format, and everyone's designs... > > Note that the above method used in version 7.2 does indeed break both the > technology file format (which I therefore advanced from version 27 to > version 28) and also the .ext file format (which is probably safe because > nobody uses the format other than magic, that I'm aware of). But I have > run the version 7.2 extresist on layouts generated under 7.1 without > everything collapsing. > > I don't really like the idea of depending on label tags for things that > magic ought to figure out by itself; in particular, it should not be > necessary to depend on "extresist" to pick out which resistors were > planned in the design and which weren't. You seem to be pretty adept > at using "extresist", though, so you may have motives other than just > using it to get around the problem of declaring resistors in your > layouts. I resorted to using the label tags in order to work around my lack of knowledge about the features of 7.2 and the pseudo-layers (thank you for enlightening me, by the way, Jeff). The extresist option worked wonderfully in cases where both sides of the extracted resistor were connected to INTERIOR nodes. When there was an exterior node, the node would be equiv'ed out of existance during extraction. This may be why I could not extract that resistor. While kicking around the pseudo-layers, I did spot an inaccurate or inconsistant pseudo-fet extraction (I have attached the file which generated the inconsistancy). You will notice that the two resistive poly lines are of the same width and length (or nearly so, depending on the extraction of the poly contact). The pseudo-fet that was generated for the ext_in poly line was of equal length, but wider than the feedback poly line. Since the line was very long, this generates a large difference between the two resistors. Hopefully, this is not an issue in 7.2. The only other thing I noticed when comparing the two resistance extraction methods was that extresist may have resulted in a slightly more accurate resistance extraction. The two things I saw holding this feature back were the complexity of extraction (an automatable multi-step procedure) and the inability to extract resistors connected to external nodes. If 7.2 has worked around these issues, I will be deep-six'ing 7.1 in the very near future. Steve
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