Hi <@U01819B63HP>, might have hit an xschem bug re...
# xschemm
Matt Venn
04/07/2024, 1:10 PMHi @Stefan Schippers, might have hit an xschem bug related to exporting netlist with lvs subckt option is on
Matt Venn
04/07/2024, 1:10 PMhere's the repo: https://github.com/TinyTapeout/tt_asw_1v8
Matt Venn
04/07/2024, 1:10 PMwith the option on I get this netlist
Matt Venn
04/07/2024, 1:11 PM Copy code
** sch_path: /home/matt/work/asic-workshop/shuttle-2404/tt-analog-switch/xschem/tt_asw_1v8.sch
.subckt tt_asw_1v8 VPWR ctrl mod bus VGND
*.PININFO VPWR:B VGND:B mod:B bus:B ctrl:I
XM4 tgon tgon_n VGND VGND sky130_fd_pr__nfet_01v8 L=0.15 W=1.5 nf=1 m=1
XM3 tgon tgon_n VPWR VPWR sky130_fd_pr__pfet_01v8 L=0.15 W=3 nf=2 m=1
XM2 tgon_n ctrl VGND VGND sky130_fd_pr__nfet_01v8 L=0.15 W=1.5 nf=1 m=1
XM1 tgon_n ctrl VPWR VPWR sky130_fd_pr__pfet_01v8 L=0.15 W=3 nf=2 m=1
XM6 bus tgon mod VGND sky130_fd_pr__nfet_01v8_lvt L=0.5 W=12 nf=4 m=1
XM5 bus tgon_n mod VPWR sky130_fd_pr__pfet_01v8_lvt L=0.5 W=21 nf=7 m=1
.ends
.endMatt Venn
04/07/2024, 1:11 PMand when it's off i get this
Matt Venn
04/07/2024, 1:12 PM Copy code
** sch_path: /home/matt/work/asic-workshop/shuttle-2404/tt_asw_1v8/xschem/tt_asw_1v8.sch
.subckt tt_asw_1v8 VPWR ctrl mod bus VGND
*.iopin VPWR
*.iopin VGND
*.iopin mod
*.iopin bus
*.ipin ctrl
XM4 tgon tgon_n VGND VGND sky130_fd_pr__nfet_01v8 L=0.15 W=1.5 nf=1 ad='int((nf+1)/2) * W/nf * 0.29' as='int((nf+2)/2) * W/nf * 0.29'
+ pd='2*int((nf+1)/2) * (W/nf + 0.29)' ps='2*int((nf+2)/2) * (W/nf + 0.29)' nrd='0.29 / W' nrs='0.29 / W' sa=0 sb=0 sd=0 mult=1 m=1
XM3 tgon tgon_n VPWR VPWR sky130_fd_pr__pfet_01v8 L=0.15 W=3 nf=2 ad='int((nf+1)/2) * W/nf * 0.29' as='int((nf+2)/2) * W/nf * 0.29'
+ pd='2*int((nf+1)/2) * (W/nf + 0.29)' ps='2*int((nf+2)/2) * (W/nf + 0.29)' nrd='0.29 / W' nrs='0.29 / W' sa=0 sb=0 sd=0 mult=1 m=1
XM2 tgon_n ctrl VGND VGND sky130_fd_pr__nfet_01v8 L=0.15 W=1.5 nf=1 ad='int((nf+1)/2) * W/nf * 0.29' as='int((nf+2)/2) * W/nf * 0.29'
+ pd='2*int((nf+1)/2) * (W/nf + 0.29)' ps='2*int((nf+2)/2) * (W/nf + 0.29)' nrd='0.29 / W' nrs='0.29 / W' sa=0 sb=0 sd=0 mult=1 m=1
XM1 tgon_n ctrl VPWR VPWR sky130_fd_pr__pfet_01v8 L=0.15 W=3 nf=2 ad='int((nf+1)/2) * W/nf * 0.29' as='int((nf+2)/2) * W/nf * 0.29'
+ pd='2*int((nf+1)/2) * (W/nf + 0.29)' ps='2*int((nf+2)/2) * (W/nf + 0.29)' nrd='0.29 / W' nrs='0.29 / W' sa=0 sb=0 sd=0 mult=1 m=1
XM6 bus tgon mod VGND sky130_fd_pr__nfet_01v8_lvt L=0.5 W='12 * 4 ' nf=4 ad='int((nf+1)/2) * W / nf * 0.29' as='int((nf+2)/2) * W / nf * 0.29'
+ pd='2*int((nf+1)/2) * (W / nf + 0.29)' ps='2*int((nf+2)/2) * (W / nf + 0.29)' nrd='0.29 / W ' nrs='0.29 / W ' sa=0 sb=0 sd=0 mult=1
+ m=1
XM5 bus tgon_n mod VPWR sky130_fd_pr__pfet_01v8_lvt L=0.5 W='21 * 7 ' nf=7 ad='int((nf+1)/2) * W / nf * 0.29' as='int((nf+2)/2) * W / nf * 0.29'
+ pd='2*int((nf+1)/2) * (W / nf + 0.29)' ps='2*int((nf+2)/2) * (W / nf + 0.29)' nrd='0.29 / W ' nrs='0.29 / W ' sa=0 sb=0 sd=0 mult=1
+ m=1
*.ends
.endMatt Venn
04/07/2024, 1:12 PMwhich matches the circuit
t
tnt
04/07/2024, 9:04 PM(note that the error might not show up in latest version of the repo, it was back when we were using the
nfs
Stefan Schippers
04/08/2024, 8:18 AM@Matt Venn @tnt thank you for reporting this bug, the W calculation for LVS is fixed upstream for *_nf symbols.
🙌 3
h
htamas
04/08/2024, 5:50 PM@Stefan Schippers There is a similar issue with 3 pin fets (i.e. those where the substrate connection is specified as an attribute instead of a pin). If I extract the netlist without the LVS option it works fine, but if I specify the LVS option the substrate connection is missing from the spice netlist. Do your upstream changes fix that or should I report it separately?
t
tnt
04/08/2024, 6:51 PM@Stefan Schippers Is the fix in xschem itself or somewhere else ? (to know what I need to update 😀 )
s
Stefan Schippers
04/08/2024, 7:59 PM@tnt @htamas the fix is in https://github.com/StefanSchippers/xschem_sky130. This repo is usually pulled in by open_pdks, anyway this is the upstream source for sky130 symbols. I have also fixed the issue with the @body connection in 3-terminal fets. Thank you so much for pointing this out!
👍 1
t
tnt
04/08/2024, 8:09 PMMmm, my PDK is always from volare, running the build every time takes forever and a lot of space. I need to figure out how to just update the symbols.
s
Stefan Schippers
04/08/2024, 8:44 PM@tnt You can just copy the symbols from here to your installation. I do the same to avoid a looooong rebuild of open_pdks.
✅ 1
t
tnt
04/08/2024, 8:45 PMThanks.
2 Views