A divide by zero exception has occurred

Look in the spectre netlist (input.scs) for the MOS device M4. Find out what the "model" name of the transistor is. Most likely this model is actually a subckt defined within the model files incuded via Setup->Model Libraries so look through those files to find the definition of the subckt. Within that there's probably an instance called r1 which is a bsource, and that has some kind of expression which has a divide by zero in it for some reason - maybe inspecting it will reveal why.

This is a bit of a guess given that i know nothing about what technology you're using, but it's a reasonably likely setup.

Regards,

Andrew.

Thanks! I found that but the expression is really complex. I think I used the same transistor in another circuit and it didn't have this problem. 

M4 (net25 net023 VDDH VDDH SUB) pa8_g5a_nbl_mac l=300n w=20u \
ad=2.486e-11 as=9.6e-12 pd=26.52u ps=41.92u nf=2 dti=0 multi=2

and this is for r1:

r1 (n1 n11) resistor r=(rdc0*wfac_res+(rd0 * exp (rd1* v(n2,n3)) * tanh(pow((1e-5+abs(v(n1,n3))),vdeff)/vdmr)
+ * (1+rdb0*v(n4,n3)) * rd_weff) *drd) *((v(n1,n3)<0)?1:0)+ (rdc0*wfac_res+(rd0rev
+ * tanh(pow(1e-5+abs(v(n2,n1)),vgeffrev)/vgmrrev) * tanh((1e-5+abs(v(n1,n3)))/(vsmr0rev
+ * exp(vsmr1rev * v(n2,n1)))) * rd_weff_rev)* drd )* (1-(v(n1,n3)<0)?1:0)
+ m=multi*nf

Without knowing the context of the message, this might be a warning that appears temporarily during calculations but doesn't adversely affect the final result.

I'd first recommend ensuring that you're using a recent version of spectre (I suspect not, given that you're using a rather elderly IC version). If the problem just shows up at the beginning, it's probably OK - but any concerns you have should be raised with the foundry who supplied the model files.

Regards,

Andrew.