FYI I just pushed to the

Question

FYI I just pushed to the <http opencircuitdesign com|opencircuitdesign com> git repo an update to magic that fixes the main issues that it had with doing full R C parasitic extraction I would be happy to have people try it out There is a tutorial that is getting increasingly out of date so the steps are as follows ```extract all ext2sim labels on ext2sim extresist tolerance 10 extresist ext2spice lvs ext2spice cthresh 0 01 ext2spice extresist on ext2spice ``` This probably works better on a flat netlist although I have run it on a shallow hierarchy standard cell layout without issues I am still working on a better solution that does not depend on the sim file format which is a flat format

Philipp Gühring · Answer

< Tim Edwards> There still seem to be a few problems The W L scaling seems too large by a factor of 10^6 and I am missing some connectivity to the IO

Tim Edwards · Answer

If you see a scalefactor where W=1 meaning 1um then that s correct for obscure reasons magic has 10000000u instead of 1 but it s the same thing This matches the option scale statement that s embedded in the SkyWater model libraries

Tim Edwards · Answer

Missing connectivity is another issue and might indicate a bug in the extresist code

John Kustin · Answer

Trying to extract some PNPs and I get the following output after extresist `Cannot open file sky130 fd pr pnp 05v5 W3p40L3p40 sim`

Tim Edwards · Answer

Did you do `ext2sim` first

John Kustin · Answer

these are my steps ```extract all ext2sim labels on ext2sim extresist tolerance 10 extresist ext2spice lvs ext2spice cthresh 0 01 ext2spice extresist on set filename $cellname set spicefilename lindex split $filename 0 ext2spice F o pex $spicefilename spice ```

Tim Edwards · Answer

Was there an error message when doing `ext2sim`

Tim Edwards · Answer

I wonder if it tried to write the sim file to the installed PDK directory or something like that

John Kustin · Answer

The ext was written to the PDK directory

Tim Edwards · Answer

Try using extract do local before extract Does that make a difference

John Kustin · Answer

I tried ```extract do local extract all``` but still get `Cannot open file sky130 fd pr pnp 05v5 W3p40L3p40 sim` I see this though `Extracting` `sky130 fd pr pnp 05v5 W3p40L3p40 into sky130 fd pr pnp 05v5 W3p40L3p40 ext `

Tim Edwards · Answer

Or I think I recall this problem which has to do with hierarchy It might not even make a difference to the output If it does then you might want to flatten the circuit before you extract extresist was originally only designed for a completely flat circuit layout and my attempts to get it working hierarchically are something of a kludge I have a development plan for it but right now it is in a state that works but may very well fail in a hierarchical circuit

Tim Edwards · Answer

If the output simulates then you can ignore the error message If the output doesn t simulate then flatten the circuit before extracting

John Kustin · Answer

When I simulate I get unknown subckt errors ```Error unknown subckt x0 xpnps 0 xsky130 fd pr pnp 05v5 w3p40l3p40 0 0|0 x0 x0 amplifier 0 gnd x0 amplifier 0 gnd x0 pnps 0 sky130 fd pr pnp 05v5 w3p40l3p40 0 7|4 emitter x0 xpnps 0 xsky130 fd pr pnp 05v5 w3p40l3p40 0 0|0 sky130 fd pr pnp 05v5 area=1 19887e+13p Simulation interrupted due to error ``` Is this what you mean by doesn t simulate

Tim Edwards · Answer

No that s a known issue that was pointed out yesterday and I am working on today Magic extracts a generic PNP model that doesn t actually exist there are only models for the two specific layouts with fixed width and length You ll need to do a string substitution on the output netlist and change device name `sky130 fd pr pnp 05v5` to `sky130 fd pr pnp 05v5 W3p40L3p40`

John Kustin · Answer

Thanks I ve noticed something else w the PNP extraction Netgen reports 2 separate PNPs but it seems like 1 PNP has absorbed all of the area ```Subcircuit pins Circuit 1 sky130 fd pr pnp 05v5 |Circuit 2 sky130 fd pr pnp 05v5 | 1 |1 2 |2 3 |3 Cell pin lists are equivalent Device classes sky130 fd pr pnp 05v5 and sky130 fd pr pnp 05v5 are equivalent Class bandgapcorev3 flat Merged 38 devices Subcircuit summary Circuit 1 bandgapCore |Circuit 2 bandgapcorev3 flat | sky130 fd pr res xhigh po 2p85 4 |sky130 fd pr res xhigh po 2p85 4 sky130 fd pr pnp 05v5 2 |sky130 fd pr pnp 05v5 2 Number of devices 6 |Number of devices 6 Number of nets 5 |Number of nets 5 ``` But when I look at the extracted netlist only 1 PNP has nonzero area ``` NGSPICE file created from bandgapcorev3 flat ext technology sky130A subckt bandgapcorev3 flat Vb Vbg Va GND X0 GND GND Vbneg sky130 fd pr pnp 05v5 area=4 79548e+14p X1 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X2 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X3 a 6870 n27666 a 13606 n30120 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X4 VbEnd GND GND sky130 fd pr res xhigh po 2p85 l=2 15e+07u X5 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X6 a 6870 n22758 a 13606 n26848 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X7 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X8 a 6870 n28484 VbgEnd GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X9 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X10 a 6870 n26030 a 13606 n23576 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X11 GND GND GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X12 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X13 GND GND GND sky130 fd pr res xhigh po 2p85 l=1 662e+07u X14 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X15 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X16 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X17 Vb Vbneg GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X18 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X19 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X20 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X21 GND GND GND sky130 fd pr res xhigh po 2p85 l=2 15e+07u X22 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X23 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X24 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X25 GND GND Va sky130 fd pr pnp 05v5 area=0p X26 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X27 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X28 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X29 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X30 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X31 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X32 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X33 GND VbgEnd GND sky130 fd pr res xhigh po 2p85 l=1 662e+07u X34 GND GND GND sky130 fd pr res xhigh po 2p85 l=2 15e+07u X35 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X36 a 6870 n26030 a 13606 n29302 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X37 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X38 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X39 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X40 GND GND GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X41 VbEnd a 13606 n29302 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X42 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X43 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X44 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X45 GND GND GND sky130 fd pr res xhigh po 2p85 l=1 662e+07u X46 a 6870 n21122 Vb GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X47 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X48 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X49 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X50 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X51 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X52 a 6870 n27666 a 13606 n25212 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X53 a 6870 n21940 Va GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X54 a 6870 n22758 Vbg GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X55 VaEnd a 13606 n30120 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X56 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X57 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X58 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X59 a 6870 n28484 a 13606 n26848 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X60 VaEnd GND GND sky130 fd pr res xhigh po 2p85 l=2 15e+07u X61 a 6870 n21940 a 13606 n25212 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u X62 GND GND Vbneg sky130 fd pr pnp 05v5 area=0p X63 a 6870 n21122 a 13606 n23576 GND sky130 fd pr res xhigh po 2p85 l=3 152e+07u ends``` There should be 1 single PNP connected to net Va and the other parallel PNPs connected to Vbneg How can it be that 2 distinct PNPs were found yet only one has any area

John Kustin · Answer

If there netgen detected 2 distinct PNP s then I d expect 2 extracted PNP s with nonzero area

Tim Edwards · Answer

It s not critical here because the W3p40L3p40 model has a fixed area Magic is totalling all area on a single net so you should run `ext2spice` with the ` d` option distributed area perimeter

John Kustin · Answer

Oh right As long as the number of extracted devices and their connected nets are correct the behavior will be right

Tim Edwards · Answer

I hadn t really considered what the lumped area method would do to devices like bipolars My fix if I get around to it today would add the device size suffix to the model and also remove the area= from the line because the area is hard coded into the subcircuit and should not be passed as a parameter I m honestly not sure if the behavior will be right or not It depends on whether the area parameter actually gets seen and parsed and overrides the default or not and if so whether the gummel poon model will just basically cause a zero area device to not exist So lots of unanswered questions

John Kustin · Answer

Makes sense I think I raised the same question on area here <https skywater pdk slack com archives C016HUV935L p1621315865013500>

John Kustin · Answer

Anyway I m trying to run this script on a completely flat design and magic segfaults ```extract do local extract all ext2sim labels on ext2sim extresist tolerance 10 extresist ext2spice lvs ext2spice cthresh 0 01 ext2spice extresist on set filename $cellname set spicefilename lindex split $filename 0 ext2spice d F o pex $spicefilename spice ``` The weird thing is if I type these commands in line by line I avoid the segfault Any idea why

Tim Edwards · Answer

No idea If you can bundle up a reproducible case I ll look into it