Hi, I hope you all are well. I'm currently working to characterize libraries using spice. I was using LTSPICE to find delays of a particular cell. For finding delay associated with the cell (cell_rise) I was manually dragging the cursor on 50% of the input voltage waveform and reporting the time, then repeating the same procedure to 50% of the output voltage waveform and minus them at the end to have a cell_delay. This is quite hectic as I need to record every cell_delay with a lot of input slews vs capacitive loads. Now I'm using NGSPICE, I've tried .meas directive to find such delays but in vain. Below is my spice deck with commented .meas directive.

* SPICE3 file created from sky130_inv.ext - technology: sky130A

.option scale=0.01u

.option TEMP=25C

.include ./pshort.lib

.include ./nshort.lib

//.subckt sky130_inv A Y VPWR VGND

M1000 Y A VPWR VPWR pshort_model.0 w=55 l=23

+  ad=2145 pd=188 as=2255 ps=192

M1001 Y A VGND VGND nshort_model.0 w=35 l=23

+  ad=1435 pd=152 as=1365 ps=148

VDD VPWR 0 1.8V

VSS VGND 0 0V

Va A VGND PULSE(0V 1.8V 2ns 1.5000000000ns 1.5000000000ns 2ns 7ns)

C0 Y A 0.05fF

C1 VPWR Y 0.10fF

C2 VPWR A 0.06fF

C3 Y 0 0.21fF

C4 VPWR 0 0.59fF

CL Y 0 0.1812840000pF

//.ends

.tran 1n 60n

.control

run

*write slew.out v(A)

*meas tran vout PP V(A)

*meas TRAN Vavg AVG V(A)

*meas tran ipdelay WHEN V(A)=0.9V

*meas tran opdelay WHEN V(Y)=0.9V

*let cell=opdelay-ipdelay

*print cell

plot A Y

set color0=white

set xbrushwidth=2

.endc

.end

I need help on how to measure cell_rise and cell_fall using ngspice commands and automatically write them in a .txt file? I'll remain highly thankful if you've a lead to the problem.

you need to use TRIG and TARG commands along with .meas

Hi Varun, It was really helpful. Thanks alot. Can you please let me know from where this excerpt from? It is outstanding. I'm interested to read this whole book/document.

in this book spice simulation part,its very nice please refer it

Thanks, Varun.