diff --git a/xschem/.spiceinit b/xschem/.spiceinit
new file mode 100644
index 0000000..e6a73aa
--- /dev/null
+++ b/xschem/.spiceinit
@@ -0,0 +1,5 @@
+* ngspice initialization for sky130
+* assert BSIM compatibility mode with "nf" vs. "W"
+set ngbehavior=hsa
+* "nomodcheck" speeds up loading time
+set ng_nomodcheck
diff --git a/xschem/current_test.spice b/xschem/current_test.spice
new file mode 100644
index 0000000..1df1edd
--- /dev/null
+++ b/xschem/current_test.spice
@@ -0,0 +1,86 @@
+*---------------------------------------------------------------------------
+* SPDX-FileCopyrightText: 2020 Efabless Corporation
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     https://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*
+* SPDX-License-Identifier: Apache-2.0
+*---------------------------------------------------------------------------
+* Simple POR circuit for Caravel current mirror test
+*-------------------------------------------------------------------
+
+.param mc_switch=0
+.lib /usr/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice tt
+
+* Note: 20 resistors of length 25um connected in series
+Xres1 vdda vin vss sky130_fd_pr__res_xhigh_po_0p69 l=500
+Xres2 vin vss vss sky130_fd_pr__res_xhigh_po_0p69 l=149
+
+* voltage sources at 0V for measuring current in each branch
+
+Vm1 vssm1 vss   DC=0
+Vm2 vdda  vddm2 DC=0
+Vm3 vdda  vddm3 DC=0
+Vm4 vssm4 vss   DC=0
+Vm5 vssm5 vss   DC=0
+Vm6 vdda  vddm6 DC=0
+Vm7 vdda  vddm7 DC=0
+
+*   D     G     S     B
+Xm1 casc1 vin   vssm1 vss  sky130_fd_pr__nfet_g5v0d10v5 w=2 l=0.8 m=1
+Xc1 mir1  casc1 casc1 vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=1
+Xm2 mir1  mir1  vddm2 vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=8
+Xm3 mir2  mir1  vddm3 vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=1
+Xc2 casc2 casc1 mir2  vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=1
+Xm4 casc2 casc2 vssm4 vss  sky130_fd_pr__nfet_g5v0d10v5 w=2 l=0.8 m=7
+Xm5 casc3 casc2 vssm5 vss  sky130_fd_pr__nfet_g5v0d10v5 w=2 l=0.8 m=1
+Xc3 mir3  casc3 casc3 vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=1
+Xm6 mir3  mir3  vddm6 vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=7
+Xm7 mir4  mir3  vddm7 vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=1
+Xc4 vcap  casc3 mir4  vdda sky130_fd_pr__pfet_g5v0d10v5 w=2 l=0.8 m=1
+
+* Check branch currents in each mirror branch.
+* 1st branch should be 240nA
+* 2nd branch should be  30nA
+* 3rd branch should be   4.3nA
+* 4th branch should be 612pA
+*
+* Result:  vin sits at 0.7590 (close to 0.7575 target)
+* I(Vm1/2) = 202.80 nA
+* I(Vm3/4) =  26.10 nA	(should be /8) actually /7.77
+* I(Vm5/6) =   4.58 nA	(should be /7) actually /5.70
+* I(Vm7)   =   0.67 nA	(should be /7) actually /6.80
+
+*----------------------------
+* Testbench circuit
+*----------------------------
+Vpwr vdda vss DC=3.3
+Rgnd vss 0 0.01
+Rload vcap vss 1MEG
+*----------------------------
+
+*----------------------------
+* Testbench control
+*----------------------------
+.control
+op
+print V(vin)
+print I(Vm1)
+print I(Vm2)
+print I(Vm3)
+print I(Vm4)
+print I(Vm5)
+print I(Vm6)
+print I(Vm7)
+.endc
+
+.end
+
diff --git a/xschem/example_por.sch b/xschem/example_por.sch
new file mode 100644
index 0000000..0dfa849
--- /dev/null
+++ b/xschem/example_por.sch
@@ -0,0 +1,300 @@
+v {xschem version=2.9.9 file_version=1.2 }
+G {}
+K {}
+V {}
+S {}
+E {}
+L 4 3370 -60 3390 -60 {}
+L 4 3390 -60 3390 80 {}
+L 4 3370 80 3390 80 {}
+T {Current step-down mirror} 2270 140 0 0 0.4 0.4 {}
+T {Charge accumulator} 2650 140 0 0 0.4 0.4 {}
+T {Voltage divider} 1860 140 0 0 0.4 0.4 {}
+T {Schmitt trigger} 2930 -200 0 0 0.4 0.4 {}
+T {150 / 650 * 3.3V = 0.76V} 1860 180 0 0 0.4 0.4 {}
+T {step down 8x} 2130 -430 0 0 0.4 0.4 {}
+T {step down 7x} 2330 80 0 0 0.4 0.4 {}
+T {step down 7x} 2520 -430 0 0 0.4 0.4 {}
+T {1.8V domain outputs} 3400 0 0 0 0.4 0.4 {}
+T {3.3V domain output} 3410 -140 0 0 0.4 0.4 {}
+T {392 : 1} 2270 180 0 0 0.4 0.4 {}
+T {Simple power-on-reset circuit
+calibrated to 500us nominal delay
+no temperature compensation} 1950 -570 0 0 0.6 0.6 {}
+N 2500 -310 2500 -270 { lab=#net2}
+N 2500 -210 2500 -100 { lab=#net3}
+N 2300 -40 2300 20 { lab=#net4}
+N 2300 80 2300 110 { lab=vss}
+N 2360 110 2500 110 { lab=vss}
+N 2500 80 2500 110 { lab=vss}
+N 2400 50 2460 50 { lab=#net4}
+N 2360 -400 2500 -400 { lab=vdd3v3}
+N 2500 -400 2500 -370 { lab=vdd3v3}
+N 2500 -400 2790 -400 { lab=vdd3v3}
+N 2300 -10 2370 -10 { lab=#net4}
+N 2370 -10 2370 50 { lab=#net4}
+N 2500 -290 2570 -290 { lab=#net2}
+N 2570 -340 2570 -290 { lab=#net2}
+N 2540 -340 2570 -340 { lab=#net2}
+N 2500 -190 2570 -190 { lab=#net3}
+N 2570 -240 2570 -190 { lab=#net3}
+N 2540 -240 2570 -240 { lab=#net3}
+N 2240 110 2360 110 { lab=vss}
+N 2500 110 2630 110 { lab=vss}
+N 2500 50 2630 50 { lab=vss}
+N 2110 110 2240 110 { lab=vss}
+N 1930 60 1930 110 { lab=vss}
+N 1930 -160 1930 0 { lab=#net6}
+N 1930 -400 1930 -220 { lab=vdd3v3}
+N 2110 -400 2360 -400 { lab=vdd3v3}
+N 1880 -190 1910 -190 { lab=vss}
+N 1880 -190 1880 110 { lab=vss}
+N 1880 110 1930 110 { lab=vss}
+N 1880 30 1910 30 { lab=vss}
+N 2300 -310 2300 -270 { lab=#net7}
+N 2300 -400 2300 -370 { lab=vdd3v3}
+N 2300 -140 2300 -100 { lab=#net5}
+N 2340 50 2400 50 { lab=#net4}
+N 2300 -210 2300 -140 { lab=#net5}
+N 2100 80 2100 110 { lab=vss}
+N 2100 110 2110 110 { lab=vss}
+N 2050 50 2060 50 { lab=#net6}
+N 2050 -70 2050 50 { lab=#net6}
+N 1930 -70 2050 -70 { lab=#net6}
+N 1930 -400 2110 -400 { lab=vdd3v3}
+N 2100 -400 2100 -370 { lab=vdd3v3}
+N 2100 -310 2100 -270 { lab=#net8}
+N 2100 -210 2100 20 { lab=#net9}
+N 2100 50 2300 50 { lab=vss}
+N 2200 50 2200 110 { lab=vss}
+N 2140 -240 2260 -240 { lab=#net9}
+N 2140 -340 2260 -340 { lab=#net8}
+N 2100 -290 2180 -290 { lab=#net8}
+N 2180 -340 2180 -290 { lab=#net8}
+N 2100 -180 2180 -180 { lab=#net9}
+N 2180 -240 2180 -180 { lab=#net9}
+N 1930 -240 2100 -240 { lab=vdd3v3}
+N 1930 -340 2100 -340 { lab=vdd3v3}
+N 1930 110 2100 110 { lab=vss}
+N 2300 -240 2500 -240 { lab=vdd3v3}
+N 2300 -340 2500 -340 { lab=vdd3v3}
+N 2400 -340 2400 -240 { lab=vdd3v3}
+N 2400 -400 2400 -340 { lab=vdd3v3}
+N 2570 -240 2650 -240 { lab=#net3}
+N 2570 -340 2650 -340 { lab=#net2}
+N 2690 -400 2690 -370 { lab=vdd3v3}
+N 2790 -400 2790 -340 { lab=vdd3v3}
+N 2690 -340 2790 -340 { lab=vdd3v3}
+N 2690 -240 2790 -240 { lab=vdd3v3}
+N 2790 -340 2790 -240 { lab=vdd3v3}
+N 2690 -310 2690 -270 { lab=#net10}
+N 2690 -210 2690 -150 { lab=#net11}
+N 1830 30 1880 30 { lab=vss}
+N 1810 60 1810 110 { lab=vss}
+N 1810 110 1880 110 { lab=vss}
+N 1810 -70 1810 0 { lab=vss}
+N 1810 -70 1880 -70 { lab=vss}
+N 2690 -150 2690 -70 { lab=#net11}
+N 2820 -130 2820 -70 { lab=#net11}
+N 2690 -130 2820 -130 { lab=#net11}
+N 2630 110 2820 110 { lab=vss}
+N 2820 -10 2820 110 { lab=vss}
+N 2690 -10 2690 110 { lab=vss}
+N 2820 -130 2980 -130 { lab=#net11}
+N 3060 -130 3130 -130 { lab=#net12}
+N 3090 -130 3090 60 { lab=#net12}
+N 3090 60 3130 60 { lab=#net12}
+N 3090 -40 3130 -40 { lab=#net12}
+N 3210 -130 3300 -130 { lab=porb_h}
+N 3210 -40 3300 -40 { lab=porb_l}
+N 3210 60 3300 60 { lab=por_l}
+N 2790 -400 2840 -400 { lab=vdd3v3}
+N 2820 110 2870 110 { lab=vss}
+N 2630 50 2690 50 {}
+N 2300 -100 2300 -40 {}
+N 2500 -100 2500 -30 {}
+N 2500 -30 2500 20 {}
+C {sky130_fd_pr/cap_mim_m3_1.sym} 2690 -40 0 0 {name=C1 model=cap_mim_m3_1 W=30 L=30 MF=1 spiceprefix=X}
+C {sky130_fd_pr/cap_mim_m3_2.sym} 2820 -40 0 0 {name=C2 model=cap_mim_m3_2 W=30 L=30 MF=1 spiceprefix=X}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2280 -240 0 0 {name=M1
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/nfet_g5v0d10v5.sym} 2480 50 0 0 {name=M2
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=nfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/res_xhigh_po_0p69.sym} 1930 -190 0 0 {name=R1
+W=0.69
+L=500
+model=res_xhigh_po_0p69
+spiceprefix=X
+mult=1}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2280 -340 0 0 {name=M4
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/nfet_g5v0d10v5.sym} 2320 50 0 1 {name=M5
+L=0.8
+W=14
+nf=7
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=nfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/res_xhigh_po_0p69.sym} 1930 30 0 0 {name=R2
+W=0.69
+L=150
+model=res_xhigh_po_0p69
+spiceprefix=X
+mult=1}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2520 -240 0 1 {name=M7
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2520 -340 0 1 {name=M8
+L=0.8
+W=14
+nf=7
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/nfet_g5v0d10v5.sym} 2080 50 0 0 {name=M10
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=nfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2120 -240 0 1 {name=M9
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2120 -340 0 1 {name=M11
+L=0.8
+W=16
+nf=8
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2670 -340 0 0 {name=M12
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/pfet_g5v0d10v5.sym} 2670 -240 0 0 {name=M13
+L=0.8
+W=2
+nf=1
+mult=1
+ad="'int((nf+1)/2) * W/nf * 0.29'" 
+pd="'2*int((nf+1)/2) * (W/nf + 0.29)'"
+as="'int((nf+2)/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
+model=pfet_g5v0d10v5
+spiceprefix=X
+}
+C {sky130_fd_pr/res_xhigh_po_0p69.sym} 1810 30 0 1 {name=R3
+W=0.69
+L=25
+model=res_xhigh_po_0p69
+spiceprefix=X
+mult=2}
+C {sky130_stdcells/buf_8.sym} 3170 -130 0 0 {name=x2 VGND=vss VNB=vss VPB=vdd3v3 VPWR=vdd3v3 prefix=sky130_fd_sc_hvl__ }
+C {sky130_stdcells/buf_8.sym} 3170 -40 0 0 {name=x3 VGND=vss VNB=vss VPB=vdd1v8 VPWR=vdd1v8 prefix=sky130_fd_sc_hvl__ }
+C {sky130_stdcells/inv_8.sym} 3170 60 0 0 {name=x4 VGND=vss VNB=vss VPB=vdd1v8 VPWR=vdd1v8 prefix=sky130_fd_sc_hvl__ }
+C {sky130_stdcells/buf_1.sym} 3020 -130 0 0 {name=x5 VGND=vss VNB=vss VPB=vdd3v3 VPWR=vdd3v3 prefix=sky130_fd_sc_hvl__schmitt }
+C {devices/iopin.sym} 2840 -400 0 0 {name=p1 lab=vdd3v3}
+C {devices/iopin.sym} 2870 110 0 0 {name=p2 lab=vss}
+C {devices/opin.sym} 3300 -130 0 0 {name=p3 lab=porb_h}
+C {devices/opin.sym} 3300 -40 0 0 {name=p4 lab=porb_l}
+C {devices/opin.sym} 3300 60 0 0 {name=p5 lab=por_l}
+C {devices/iopin.sym} 2840 -330 0 0 {name=p6 lab=vdd1v8}
diff --git a/xschem/example_por.sym b/xschem/example_por.sym
new file mode 100644
index 0000000..e3875f5
--- /dev/null
+++ b/xschem/example_por.sym
@@ -0,0 +1,33 @@
+v {xschem version=2.9.9 file_version=1.2 }
+G {}
+K {type=subcircuit
+format="@name @pinlist @symname"
+template="name=x1"
+}
+V {}
+S {}
+E {}
+L 4 -130 -60 130 -60 {}
+L 4 -130 60 130 60 {}
+L 4 -130 -60 -130 60 {}
+L 4 130 -60 130 60 {}
+L 4 130 -30 150 -30 {}
+L 4 130 0 150 0 {}
+L 4 130 30 150 30 {}
+L 7 -30 -80 -30 -60 {}
+L 7 30 -80 30 -60 {}
+L 7 0 60 0 80 {}
+B 5 -32.5 -82.5 -27.5 -77.5 {name=vdd3v3 dir=inout }
+B 5 27.5 -82.5 32.5 -77.5 {name=vdd1v8 dir=inout }
+B 5 147.5 -32.5 152.5 -27.5 {name=porb_h dir=out }
+B 5 147.5 -2.5 152.5 2.5 {name=porb_l dir=out }
+B 5 147.5 27.5 152.5 32.5 {name=por_l dir=out }
+B 5 -2.5 77.5 2.5 82.5 {name=vss dir=inout }
+T {@symname} -47.5 -6 0 0 0.3 0.3 {}
+T {@name} -25 18 0 0 0.2 0.2 {}
+T {vdd3v3} -15 -54 0 1 0.2 0.2 {}
+T {vdd1v8} 55 -54 0 1 0.2 0.2 {}
+T {porb_h} 125 -34 0 1 0.2 0.2 {}
+T {porb_l} 125 -4 0 1 0.2 0.2 {}
+T {por_l} 125 26 0 1 0.2 0.2 {}
+T {vss} 5 46 0 1 0.2 0.2 {}
diff --git a/xschem/example_por_tb.sch b/xschem/example_por_tb.sch
new file mode 100644
index 0000000..2d9ba11
--- /dev/null
+++ b/xschem/example_por_tb.sch
@@ -0,0 +1,36 @@
+v {xschem version=2.9.9 file_version=1.2 }
+G {}
+K {}
+V {}
+S {}
+E {}
+T {Testbench for simple POR} -350 -240 0 0 0.6 0.6 {}
+N -280 60 -10 60 { lab=GND}
+N -330 0 -330 60 { lab=GND}
+N -210 -0 -210 60 { lab=GND}
+N -210 -100 -210 -60 { lab=vdd3v3}
+N -210 -110 -210 -100 { lab=vdd3v3}
+N -210 -110 -40 -110 { lab=vdd3v3}
+N -40 -110 -40 -100 { lab=vdd3v3}
+N -330 -130 -330 -60 { lab=vdd1v8}
+N -280 -130 20 -130 { lab=vdd1v8}
+N 20 -130 20 -100 { lab=vdd1v8}
+N 140 -50 180 -50 { lab=porb_h}
+N 140 -20 180 -20 { lab=porb_l}
+N 140 10 180 10 { lab=por_l}
+N -220 -110 -210 -110 { lab=vdd3v3}
+N -290 -130 -280 -130 { lab=vdd1v8}
+N -330 -130 -290 -130 { lab=vdd1v8}
+N -350 -130 -330 -130 { lab=vdd1v8}
+N -330 60 -280 60 { lab=GND}
+C {example_por.sym} -10 -20 0 0 {name=x1}
+C {devices/gnd.sym} -100 60 0 0 {name=l1 lab=GND}
+C {devices/vsource.sym} -210 -30 0 0 {name=V1 value="PWL(0.0 0 100u 0 5m 3.3)"}
+C {devices/vsource.sym} -330 -30 0 0 {name=V2 value="PWL(0.0 0 300u 0 5.3m 1.8)"}
+C {devices/opin.sym} -220 -110 0 1 {name=p1 lab=vdd3v3}
+C {devices/opin.sym} -350 -130 0 1 {name=p2 lab=vdd1v8}
+C {devices/opin.sym} 180 -50 0 0 {name=p3 lab=porb_h}
+C {devices/opin.sym} 180 -20 0 0 {name=p4 lab=porb_l}
+C {devices/opin.sym} 180 10 0 0 {name=p5 lab=por_l}
+C {devices/code.sym} 140 -270 0 0 {name=s1 only_toplevel=false value=".lib /usr/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice tt"}
+C {devices/code.sym} 260 -270 0 0 {name=s2 only_toplevel=false value=".include /usr/share/pdk/sky130A/libs.ref/sky130_fd_sc_hvl/spice/sky130_fd_sc_hvl.spice"}
diff --git a/xschem/example_por_tb.spice b/xschem/example_por_tb.spice
new file mode 100644
index 0000000..5af67cf
--- /dev/null
+++ b/xschem/example_por_tb.spice
@@ -0,0 +1,82 @@
+**.subckt example_por_tb vdd3v3 vdd1v8 porb_h porb_l por_l
+.param mc_switch=0
+*.opin vdd3v3
+*.opin vdd1v8
+*.opin porb_h
+*.opin porb_l
+*.opin por_l
+x1 vdd3v3 vdd1v8 porb_h porb_l por_l GND example_por
+V1 vdd3v3 GND PWL(0.0 0 100u 0 5m 3.3)
+V2 vdd1v8 GND PWL(0.0 0 300u 0 5.3m 1.8)
+**** begin user architecture code
+
+.lib /usr/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice tt
+
+
+.include /usr/share/pdk/sky130A/libs.ref/sky130_fd_sc_hvl/spice/sky130_fd_sc_hvl.spice
+
+.control
+tran 1u 20m
+plot V(vdd3v3) V(vdd1v8) V(porb_h) V(porb_l) V(por_l)
+.endc
+
+**** end user architecture code
+**.ends
+
+* expanding   symbol:  example_por.sym # of pins=6
+* sym_path: /home/tim/gits/caravel_user_project_analog/xschem/example_por.sym
+* sch_path: /home/tim/gits/caravel_user_project_analog/xschem/example_por.sch
+.subckt example_por  vdd3v3 vdd1v8 porb_h porb_l por_l vss
+*.iopin vdd3v3
+*.iopin vss
+*.opin porb_h
+*.opin porb_l
+*.opin por_l
+*.iopin vdd1v8
+XC1 net9 vss sky130_fd_pr__cap_mim_m3_1 W=30 L=30 MF=1 m=1
+XC2 net9 vss sky130_fd_pr__cap_mim_m3_2 W=30 L=30 MF=1 m=1
+XM1 net3 net7 net5 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM2 net2 net3 vss vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=2 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 
+XR1 net4 vdd3v3 vss sky130_fd_pr__res_xhigh_po_0p69 W=0.69 L=500 mult=1 m=1
+XM4 net5 net6 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM5 net3 net3 vss vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=14 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 
+XR2 vss net4 vss sky130_fd_pr__res_xhigh_po_0p69 W=0.69 L=150 mult=1 m=1
+XM7 net2 net2 net1 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM8 net1 net1 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=14 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 
+XM10 net7 net4 vss vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=2 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 
+XM9 net7 net7 net6 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM11 net6 net6 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=16 nf=8 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 
+XM12 net8 net1 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM13 net9 net2 net8 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XR3 vss vss vss sky130_fd_pr__res_xhigh_po_0p69 W=0.69 L=25 mult=2 m=2
+x2 net10 vss vss vdd3v3 vdd3v3 porb_h sky130_fd_sc_hvl__buf_8
+x3 net10 vss vss vdd1v8 vdd1v8 porb_l sky130_fd_sc_hvl__buf_8
+x4 net10 vss vss vdd1v8 vdd1v8 por_l sky130_fd_sc_hvl__inv_8
+x5 net9 vss vss vdd3v3 vdd3v3 net10 sky130_fd_sc_hvl__schmittbuf_1
+.ends
+
+.GLOBAL GND
+** flattened .save nodes
+.end
diff --git a/xschem/example_por_tb.spice.orig b/xschem/example_por_tb.spice.orig
new file mode 100644
index 0000000..069c74d
--- /dev/null
+++ b/xschem/example_por_tb.spice.orig
@@ -0,0 +1,88 @@
+**.subckt example_por_tb vdd3v3 vdd1v8 porb_h porb_l por_l
+.param mc_switch=0
+*.opin vdd3v3
+*.opin vdd1v8
+*.opin porb_h
+*.opin porb_l
+*.opin por_l
+x1 vdd3v3 vdd1v8 porb_h porb_l por_l GND example_por
+V1 vdd3v3 GND PWL(0.0 0 100u 0 5m 3.3)
+V2 vdd1v8 GND PWL(0.0 0 300u 0 5.3m 1.8)
+**** begin user architecture code
+
+.lib /usr/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice tt
+
+
+.include /usr/share/pdk/sky130A/libs.ref/sky130_fd_sc_hvl/spice/sky130_fd_sc_hvl.spice
+
+.control
+tran 1u 20m
+plot V(vdd3v3) V(vdd1v8) V(porb_h) V(porb_l) V(por_l)
+.endc
+
+**** end user architecture code
+**.ends
+
+* expanding   symbol:  example_por.sym # of pins=6
+* sym_path: /home/tim/gits/caravel_user_project_analog/xschem/example_por.sym
+* sch_path: /home/tim/gits/caravel_user_project_analog/xschem/example_por.sch
+.subckt example_por  vdd3v3 vdd1v8 porb_h porb_l por_l vss
+*.iopin vdd3v3
+*.iopin vss
+*.opin porb_h
+*.opin porb_l
+*.opin por_l
+*.iopin vdd1v8
+XC1 net11 vss sky130_fd_pr__cap_mim_m3_1 W=30 L=30 MF=1 m=1
+XC2 net11 vss sky130_fd_pr__cap_mim_m3_2 W=30 L=30 MF=1 m=1
+XM1 net5 net9 net7 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM2 net1 net4 vss vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=2 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 
+XR1 net6 vdd3v3 vss sky130_fd_pr__res_xhigh_po_0p69 W=0.69 L=500 mult=1 m=1
+XM3 net3 net5 net1 vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=2 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 
+XM4 net7 net8 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM5 net4 net4 vss vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=14 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 
+XM6 net5 net5 net4 vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=2 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 
+XR2 vss net6 vss sky130_fd_pr__res_xhigh_po_0p69 W=0.69 L=150 mult=1 m=1
+XM7 net3 net3 net2 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM8 net2 net2 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=14 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 
+XM10 net9 net6 vss vss sky130_fd_pr__nfet_g5v0d10v5 L=0.8 W=2 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 
+XM9 net9 net9 net8 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM11 net8 net8 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=16 nf=8 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 
+XM12 net10 net2 vdd3v3 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XM13 net11 net3 net10 vdd3v3 sky130_fd_pr__pfet_g5v0d10v5 L=0.8 W=2 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 
+XR3 vss vss vss sky130_fd_pr__res_xhigh_po_0p69 W=0.69 L=25 mult=2 m=2
+x2 net12 vss vss vdd3v3 vdd3v3 porb_h sky130_fd_sc_hvl__buf_8
+x3 net12 vss vss vdd1v8 vdd1v8 porb_l sky130_fd_sc_hvl__buf_8
+x4 net12 vss vss vdd1v8 vdd1v8 por_l sky130_fd_sc_hvl__inv_8
+x5 net11 vss vss vdd3v3 vdd3v3 net12 sky130_fd_sc_hvl__schmittbuf_1
+.ends
+
+.GLOBAL GND
+** flattened .save nodes
+.end
diff --git a/xschem/test.data b/xschem/test.data
new file mode 100644
index 0000000..c9cde37
--- /dev/null
+++ b/xschem/test.data
@@ -0,0 +1,101 @@
+ 7.00000000e-01 -8.93059159e-08  7.00000000e-01  7.00000000e-01 
+ 7.01000000e-01 -9.08452852e-08  7.01000000e-01  7.01000000e-01 
+ 7.02000000e-01 -9.24385447e-08  7.02000000e-01  7.02000000e-01 
+ 7.03000000e-01 -9.40459956e-08  7.03000000e-01  7.03000000e-01 
+ 7.04000000e-01 -9.56814959e-08  7.04000000e-01  7.04000000e-01 
+ 7.05000000e-01 -9.73455368e-08  7.05000000e-01  7.05000000e-01 
+ 7.06000000e-01 -9.90386085e-08  7.06000000e-01  7.06000000e-01 
+ 7.07000000e-01 -1.00761227e-07  7.07000000e-01  7.07000000e-01 
+ 7.08000000e-01 -1.02513882e-07  7.08000000e-01  7.08000000e-01 
+ 7.09000000e-01 -1.04297110e-07  7.09000000e-01  7.09000000e-01 
+ 7.10000000e-01 -1.06111443e-07  7.10000000e-01  7.10000000e-01 
+ 7.11000000e-01 -1.07957415e-07  7.11000000e-01  7.11000000e-01 
+ 7.12000000e-01 -1.09835552e-07  7.12000000e-01  7.12000000e-01 
+ 7.13000000e-01 -1.11746436e-07  7.13000000e-01  7.13000000e-01 
+ 7.14000000e-01 -1.13690603e-07  7.14000000e-01  7.14000000e-01 
+ 7.15000000e-01 -1.15668634e-07  7.15000000e-01  7.15000000e-01 
+ 7.16000000e-01 -1.17681129e-07  7.16000000e-01  7.16000000e-01 
+ 7.17000000e-01 -1.19728657e-07  7.17000000e-01  7.17000000e-01 
+ 7.18000000e-01 -1.21811839e-07  7.18000000e-01  7.18000000e-01 
+ 7.19000000e-01 -1.23931259e-07  7.19000000e-01  7.19000000e-01 
+ 7.20000000e-01 -1.26087554e-07  7.20000000e-01  7.20000000e-01 
+ 7.21000000e-01 -1.28281358e-07  7.21000000e-01  7.21000000e-01 
+ 7.22000000e-01 -1.30513286e-07  7.22000000e-01  7.22000000e-01 
+ 7.23000000e-01 -1.32784003e-07  7.23000000e-01  7.23000000e-01 
+ 7.24000000e-01 -1.35094165e-07  7.24000000e-01  7.24000000e-01 
+ 7.25000000e-01 -1.37444453e-07  7.25000000e-01  7.25000000e-01 
+ 7.26000000e-01 -1.39835535e-07  7.26000000e-01  7.26000000e-01 
+ 7.27000000e-01 -1.42268085e-07  7.27000000e-01  7.27000000e-01 
+ 7.28000000e-01 -1.44742842e-07  7.28000000e-01  7.28000000e-01 
+ 7.29000000e-01 -1.47260486e-07  7.29000000e-01  7.29000000e-01 
+ 7.30000000e-01 -1.49821761e-07  7.30000000e-01  7.30000000e-01 
+ 7.31000000e-01 -1.52427364e-07  7.31000000e-01  7.31000000e-01 
+ 7.32000000e-01 -1.55078077e-07  7.32000000e-01  7.32000000e-01 
+ 7.33000000e-01 -1.57774611e-07  7.33000000e-01  7.33000000e-01 
+ 7.34000000e-01 -1.60517775e-07  7.34000000e-01  7.34000000e-01 
+ 7.35000000e-01 -1.63308337e-07  7.35000000e-01  7.35000000e-01 
+ 7.36000000e-01 -1.66147061e-07  7.36000000e-01  7.36000000e-01 
+ 7.37000000e-01 -1.69034765e-07  7.37000000e-01  7.37000000e-01 
+ 7.38000000e-01 -1.71972266e-07  7.38000000e-01  7.38000000e-01 
+ 7.39000000e-01 -1.74960357e-07  7.39000000e-01  7.39000000e-01 
+ 7.40000000e-01 -1.77999888e-07  7.40000000e-01  7.40000000e-01 
+ 7.41000000e-01 -1.81091703e-07  7.41000000e-01  7.41000000e-01 
+ 7.42000000e-01 -1.84236664e-07  7.42000000e-01  7.42000000e-01 
+ 7.43000000e-01 -1.87435634e-07  7.43000000e-01  7.43000000e-01 
+ 7.44000000e-01 -1.90689493e-07  7.44000000e-01  7.44000000e-01 
+ 7.45000000e-01 -1.93999127e-07  7.45000000e-01  7.45000000e-01 
+ 7.46000000e-01 -1.97365464e-07  7.46000000e-01  7.46000000e-01 
+ 7.47000000e-01 -2.00789378e-07  7.47000000e-01  7.47000000e-01 
+ 7.48000000e-01 -2.04271837e-07  7.48000000e-01  7.48000000e-01 
+ 7.49000000e-01 -2.07813739e-07  7.49000000e-01  7.49000000e-01 
+ 7.50000000e-01 -2.11416073e-07  7.50000000e-01  7.50000000e-01 
+ 7.51000000e-01 -2.15079797e-07  7.51000000e-01  7.51000000e-01 
+ 7.52000000e-01 -2.18805863e-07  7.52000000e-01  7.52000000e-01 
+ 7.53000000e-01 -2.22595278e-07  7.53000000e-01  7.53000000e-01 
+ 7.54000000e-01 -2.26449036e-07  7.54000000e-01  7.54000000e-01 
+ 7.55000000e-01 -2.30368144e-07  7.55000000e-01  7.55000000e-01 
+ 7.56000000e-01 -2.34353630e-07  7.56000000e-01  7.56000000e-01 
+ 7.57000000e-01 -2.38406548e-07  7.57000000e-01  7.57000000e-01 
+ 7.58000000e-01 -2.42527913e-07  7.58000000e-01  7.58000000e-01 
+ 7.59000000e-01 -2.46718795e-07  7.59000000e-01  7.59000000e-01 
+ 7.60000000e-01 -2.50980278e-07  7.60000000e-01  7.60000000e-01 
+ 7.61000000e-01 -2.55313430e-07  7.61000000e-01  7.61000000e-01 
+ 7.62000000e-01 -2.59719344e-07  7.62000000e-01  7.62000000e-01 
+ 7.63000000e-01 -2.64199148e-07  7.63000000e-01  7.63000000e-01 
+ 7.64000000e-01 -2.68753946e-07  7.64000000e-01  7.64000000e-01 
+ 7.65000000e-01 -2.73384860e-07  7.65000000e-01  7.65000000e-01 
+ 7.66000000e-01 -2.78093044e-07  7.66000000e-01  7.66000000e-01 
+ 7.67000000e-01 -2.82879650e-07  7.67000000e-01  7.67000000e-01 
+ 7.68000000e-01 -2.87745826e-07  7.68000000e-01  7.68000000e-01 
+ 7.69000000e-01 -2.92692776e-07  7.69000000e-01  7.69000000e-01 
+ 7.70000000e-01 -2.97721660e-07  7.70000000e-01  7.70000000e-01 
+ 7.71000000e-01 -3.02833688e-07  7.71000000e-01  7.71000000e-01 
+ 7.72000000e-01 -3.08030053e-07  7.72000000e-01  7.72000000e-01 
+ 7.73000000e-01 -3.13311974e-07  7.73000000e-01  7.73000000e-01 
+ 7.74000000e-01 -3.18680710e-07  7.74000000e-01  7.74000000e-01 
+ 7.75000000e-01 -3.24137468e-07  7.75000000e-01  7.75000000e-01 
+ 7.76000000e-01 -3.29683509e-07  7.76000000e-01  7.76000000e-01 
+ 7.77000000e-01 -3.35320078e-07  7.77000000e-01  7.77000000e-01 
+ 7.78000000e-01 -3.41048451e-07  7.78000000e-01  7.78000000e-01 
+ 7.79000000e-01 -3.46869908e-07  7.79000000e-01  7.79000000e-01 
+ 7.80000000e-01 -3.52785731e-07  7.80000000e-01  7.80000000e-01 
+ 7.81000000e-01 -3.58797218e-07  7.81000000e-01  7.81000000e-01 
+ 7.82000000e-01 -3.64905663e-07  7.82000000e-01  7.82000000e-01 
+ 7.83000000e-01 -3.71112381e-07  7.83000000e-01  7.83000000e-01 
+ 7.84000000e-01 -3.77418703e-07  7.84000000e-01  7.84000000e-01 
+ 7.85000000e-01 -3.83825919e-07  7.85000000e-01  7.85000000e-01 
+ 7.86000000e-01 -3.90335390e-07  7.86000000e-01  7.86000000e-01 
+ 7.87000000e-01 -3.96948455e-07  7.87000000e-01  7.87000000e-01 
+ 7.88000000e-01 -4.03666461e-07  7.88000000e-01  7.88000000e-01 
+ 7.89000000e-01 -4.10490750e-07  7.89000000e-01  7.89000000e-01 
+ 7.90000000e-01 -4.17422681e-07  7.90000000e-01  7.90000000e-01 
+ 7.91000000e-01 -4.24463629e-07  7.91000000e-01  7.91000000e-01 
+ 7.92000000e-01 -4.31614946e-07  7.92000000e-01  7.92000000e-01 
+ 7.93000000e-01 -4.38878017e-07  7.93000000e-01  7.93000000e-01 
+ 7.94000000e-01 -4.46254218e-07  7.94000000e-01  7.94000000e-01 
+ 7.95000000e-01 -4.53744916e-07  7.95000000e-01  7.95000000e-01 
+ 7.96000000e-01 -4.61351506e-07  7.96000000e-01  7.96000000e-01 
+ 7.97000000e-01 -4.69075369e-07  7.97000000e-01  7.97000000e-01 
+ 7.98000000e-01 -4.76917893e-07  7.98000000e-01  7.98000000e-01 
+ 7.99000000e-01 -4.84880471e-07  7.99000000e-01  7.99000000e-01 
+ 8.00000000e-01 -4.92964482e-07  8.00000000e-01  8.00000000e-01 
diff --git a/xschem/threshold_test_tb.spice b/xschem/threshold_test_tb.spice
new file mode 100644
index 0000000..849a0f5
--- /dev/null
+++ b/xschem/threshold_test_tb.spice
@@ -0,0 +1,47 @@
+*---------------------------------------------------------------------------
+* SPDX-FileCopyrightText: 2020 Efabless Corporation
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     https://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*
+* SPDX-License-Identifier: Apache-2.0
+*---------------------------------------------------------------------------
+* Threshold test for POR circuit
+* Determine gate voltage at which the HV NFET draws 240nA nominal
+*
+* Result:  0.7575V
+*-------------------------------------------------------------------
+
+.param mc_switch=0
+.lib /usr/share/pdk/sky130A/libs.tech/ngspice/sky130.lib.spice tt
+
+*----------------------------
+* Testbench circuit
+*----------------------------
+Rtest vdda mir1 1MEG
+Xm1 mir1 vin vss vss sky130_fd_pr__nfet_g5v0d10v5 w=2 l=0.8
+
+Vgate vin vss DC=0
+Vpwr vdda vss DC=3.3
+Rgnd vss 0 0.1
+
+*----------------------------
+* Testbench control
+*----------------------------
+.control
+* DC sweep from 0.7 to 0.8V
+dc Vgate 0.7 0.8 0.001
+wrdata test.data Vpwr#branch vin
+
+.endc
+
+.end
+
diff --git a/xschem/xschemrc b/xschem/xschemrc
new file mode 100644
index 0000000..98fead5
--- /dev/null
+++ b/xschem/xschemrc
@@ -0,0 +1,273 @@
+#### xschemrc system configuration file
+
+#### values may be overridden by user's ~/.xschem/xschemrc configuration file
+#### or by project-local ./xschemrc
+
+###########################################################################
+#### XSCHEM INSTALLATION DIRECTORY: XSCHEM_SHAREDIR
+###########################################################################
+#### Normally there is no reason to set this variable if using standard
+#### installation. Location of files is set at compile time but may be overridden
+#### with following line:
+# set XSCHEM_SHAREDIR $env(HOME)/share/xschem
+
+###########################################################################
+#### XSCHEM SYSTEM-WIDE DESIGN LIBRARY PATHS: XSCHEM_LIBRARY_PATH
+###########################################################################
+#### If unset xschem starts with XSCHEM_LIBRARY_PATH set to the default, typically:
+# /home/schippes/.xschem/xschem_library
+# /home/schippes/share/xschem/xschem_library/devices
+# /home/schippes/share/doc/xschem/examples
+# /home/schippes/share/doc/xschem/ngspice
+# /home/schippes/share/doc/xschem/logic
+# /home/schippes/share/doc/xschem/xschem_simulator
+# /home/schippes/share/doc/xschem/binto7seg
+# /home/schippes/share/doc/xschem/pcb
+# /home/schippes/share/doc/xschem/rom8k
+
+#### Flush any previous definition
+set XSCHEM_LIBRARY_PATH {}
+#### include devices/*.sym
+append XSCHEM_LIBRARY_PATH ${XSCHEM_SHAREDIR}/xschem_library
+#### include skywater libraries. Here i use [pwd]. This works if i start xschem from here.
+append XSCHEM_LIBRARY_PATH :$env(PWD)
+append XSCHEM_LIBRARY_PATH :/usr/share/pdk/sky130A/libs.tech/xschem
+#### add ~/.xschem/xschem_library (USER_CONF_DIR is normally ~/.xschem)
+append XSCHEM_LIBRARY_PATH :$USER_CONF_DIR/xschem_library 
+
+###########################################################################
+#### SET CUSTOM COLORS FOR XSCHEM LIBRARIES MATCHING CERTAIN PATTERNS
+###########################################################################
+#### each line contains a dircolor(pattern) followed by a color
+#### color can be an ordinary name (grey, brown, blue) or a hex code {#77aaff}
+#### hex code must be enclosed in braces
+array unset dircolor
+set dircolor(sky130_fd_pr$) blue
+set dircolor(sky130_tests$) blue
+set dircolor(xschem_sky130$) blue
+set dircolor(xschem_library$) red
+set dircolor(devices$) red
+
+###########################################################################
+#### WINDOW TO OPEN ON STARTUP: XSCHEM_START_WINDOW
+###########################################################################
+#### Start without a design if no filename given on command line:
+#### To avoid absolute paths, use a path that is relative to one of the
+#### XSCHEM_LIBRARY_PATH directories. Default: empty
+set XSCHEM_START_WINDOW {sky130_tests/top.sch}
+
+###########################################################################
+#### DIRECTORY WHERE SIMULATIONS, NETLIST AND SIMULATOR OUTPUTS ARE PLACED
+###########################################################################
+#### If unset $USER_CONF_DIR/simulations is assumed (normally ~/.xschem/simulations) 
+# set netlist_dir $env(HOME)/.xschem/simulations
+set netlist_dir .
+
+###########################################################################
+#### CHANGE DEFAULT [] WITH SOME OTHER CHARACTERS FOR BUSSED SIGNALS 
+#### IN SPICE NETLISTS (EXAMPLE: DATA[7] --> DATA<7>) 
+###########################################################################
+#### default: empty (use xschem default, [ ])
+# set bus_replacement_char {<>}
+#### for XSPICE: replace square brackets as the are used for XSPICE vector nodes.
+# set bus_replacement_char {__} 
+
+###########################################################################
+#### SOME DEFAULT BEHAVIOR
+###########################################################################
+#### Allowed values:  spice, verilog, vhdl, tedax, default: spice
+# set netlist_type spice
+
+#### Some netlisting options (these are the defaults)
+# set hspice_netlist 1
+# set verilog_2001 1
+
+#### to use a fixed line with set change_lw to 0 and set some value to line_width
+#### these are the defaults
+# set line_width 0
+# set change_lw 1
+
+#### allow color postscript and svg exports. Default: 1, enable color
+# set color_ps 1
+
+#### initial size of xschem window you can specify also position with (wxh+x+y)
+#### this is the default:
+# set initial_geometry {900x600}
+
+#### if set to 0, when zooming out allow the viewport do drift toward the mouse position,
+#### allowing to move away by zooming / unzooming with mouse wheel
+#### default setting: 0
+# set unzoom_nodrift 0
+
+#### if set to 1 allow to place multiple components with same name.
+#### Warning: this is normally not allowed in any simulation netlist.
+#### default: 0, do not allow place multiple elements with same name (refdes)
+# set disable_unique_names 0
+
+#### if set to 1 continue drawing lines / wires after click
+#### default: 0
+# set persistent_command 1
+
+#### if set to 1 automatically join/trim wires while editing
+#### this may slow down on rally big designs. Can be disabled via menu 
+#### default: 0
+# set autotrim_wires 0
+
+#### set widget scaling (mainly for font display), this is useful on 4K displays
+#### default: unset (tk uses its default) > 1.0 ==> bigger 
+# set tk_scaling 1.7
+
+#### disable some symbol layers. Default: none, all layers are visible.
+# set enable_layer(5) 0 ;# example to disable pin red boxes
+
+#### enable to scale grid point size as done with lines at close zoom, default: 0
+# set big_grid_points 0
+
+###########################################################################
+#### EXPORT FORMAT TRANSLATORS, PNG AND PDF
+###########################################################################
+#### command to translate xpm to png; (assumes command takes source 
+#### and dest file as arguments, example: gm convert plot.xpm plot.png)
+#### default: {gm convert}
+# set to_png {gm convert}
+
+#### command to translate ps to pdf; (assumes command takes source
+#### and dest file as arguments, example: ps2pdf plot.ps plot.pdf)
+#### default: ps2pdf
+# set to_pdf ps2pdf
+
+###########################################################################
+#### CUSTOM GRID / SNAP VALUE SETTINGS
+###########################################################################
+#### Warning: changing these values will likely break compatibility
+#### with existing symbol libraries. Defaults: grid 20, snap 10.
+# set grid 20
+# set snap 10
+
+###########################################################################
+#### CUSTOM COLORS  MAY BE DEFINED HERE
+###########################################################################
+#  set cadlayers 22
+#  set light_colors {
+#   "#ffffff" "#0044ee" "#aaaaaa" "#222222" "#229900"
+#   "#bb2200" "#00ccee" "#ff0000" "#888800" "#00aaaa"
+#   "#880088" "#00ff00" "#0000cc" "#666600" "#557755"
+#   "#aa2222" "#7ccc40" "#00ffcc" "#ce0097" "#d2d46b"
+#   "#ef6158" "#fdb200" }
+
+#  set dark_colors {
+#   "#000000" "#00ccee" "#3f3f3f" "#cccccc" "#88dd00"
+#   "#bb2200" "#00ccee" "#ff0000" "#ffff00" "#ffffff"
+#   "#ff00ff" "#00ff00" "#0000cc" "#aaaa00" "#aaccaa"
+#   "#ff7777" "#bfff81" "#00ffcc" "#ce0097" "#d2d46b"
+#   "#ef6158" "#fdb200" }
+
+###########################################################################
+#### CAIRO STUFF
+###########################################################################
+#### Scale all fonts by this number
+# set cairo_font_scale 1.0
+
+#### default for following two is 0.85 (xscale) and 0.88 (yscale) to 
+#### match cairo font spacing
+# set nocairo_font_xscale 1.0
+#### set nocairo_font_yscale 1.0
+
+#### Scale line spacing by this number
+# set cairo_font_line_spacing 1.0
+
+#### Specify a font
+# set cairo_font_name {Sans-Serif}
+# set svg_font_name {Sans-Serif}
+
+#### Lift up text by some zoom-corrected pixels for
+#### better compatibility wrt no cairo version.
+#### Useful values in the range [-1, 3]
+# set cairo_vert_correct 0
+# set nocairo_vert_correct 0
+
+###########################################################################
+#### KEYBINDINGS
+###########################################################################
+#### General format for specifying a replacement for a keybind
+#### Replace Ctrl-d with Escape (so you wont kill the program)
+# set replace_key(Control-d) Escape
+
+#### swap w and W keybinds; Always specify Shift for capital letters
+# set replace_key(Shift-W) w
+# set replace_key(w) Shift-W
+
+###########################################################################
+#### TERMINAL
+###########################################################################
+#### default for linux: xterm
+# set terminal {xterm -geometry 100x35 -fn 9x15 -bg black -fg white -cr white -ms white }
+#### lxterminal is not OK since it will not inherit env vars: 
+#### In order to reduce memory usage and increase the performance, all instances
+#### of the lxterminal are sharing a single process. LXTerminal is part of LXDE
+
+###########################################################################
+#### EDITOR
+###########################################################################
+#### editor must not detach from launching shell (-f mandatory for gvim)
+#### default for linux: gvim -f
+# set editor {gvim -f -geometry 90x28}
+# set editor { xterm -geometry 100x40 -e nano }
+# set editor { xterm -geometry 100x40 -e pico }
+
+#### For Windows
+# set editor {notepad.exe}
+
+###########################################################################
+#### SHOW ERC INFO WINDOW (erc errors, warnings etc)
+###########################################################################
+#### default: 0 (can be enabled by menu)
+# set show_infowindow 0
+
+###########################################################################
+#### CONFIGURE COMPUTER FARM JOB REDIRECTORS FOR SIMULATIONS
+###########################################################################
+#### RTDA NC
+# set computerfarm {nc run -Il}
+#### LSF BSUB
+# set computerfarm {bsub -Is}
+
+###########################################################################
+#### TCP CONNECTION WITH GAW
+###########################################################################
+#### set gaw address for socket connection: {host port}
+#### default: set to localhost, port 2020
+# set gaw_tcp_address {localhost 2020}
+
+###########################################################################
+#### XSCHEM LISTEN TO TCP PORT
+###########################################################################
+#### set xschem listening port; default: not enabled
+# set xschem_listen_port 2021
+
+###########################################################################
+#### UTILE SPICE STIMULI DESCRIPTION LANGUAGE AND TRANSLATOR
+###########################################################################
+#### default paths are set as shown here: 
+# set utile_gui_path ${XSCHEM_SHAREDIR}/utile/utile3
+# set utile_cmd_path ${XSCHEM_SHAREDIR}/utile/utile
+
+###########################################################################
+#### TCL FILES TO LOAD AT STARTUP
+###########################################################################
+#### list of tcl files to preload.
+# lappend tcl_files ${XSCHEM_SHAREDIR}/change_index.tcl
+lappend tcl_files ${XSCHEM_SHAREDIR}/ngspice_backannotate.tcl
+lappend tcl_files /usr/share/pdk/sky130A/libs.tech/xschem/scripts/sky130_models.tcl
+###########################################################################
+#### XSCHEM TOOLBAR
+###########################################################################
+#### default: not enabled.
+# set toolbar_visible 1
+# set toolbar_horiz   1
+
+###########################################################################
+#### SKYWATER PDK SPECIFIC VARIABLES
+###########################################################################
+set SKYWATER_MODELS ~/skywater-pdk/libraries/sky130_fd_pr_ngspice/latest
+set SKYWATER_STDCELLS ~/skywater-pdk/libraries/sky130_fd_sc_hd/latest