target time is smaller than trigger time

[d4nt3]

HI:

When I run this sp file of a NOT gate:

*****************************
.include "c:\pfc final\tecnologias\Achanconery\ficheros finales\65nm_bulk.pm"
.include "c:\pfc final\tecnologias\Achanconery\ficheros finales\Biblioteca_digital.sp"

.param vdd=1.20

.param vss=0.00

.param temp=25

.param periodo=1.0n

.global vdd! vss!
**********************************
.param Lmin=65n WNmin=100n WPmin=260n

**********************************
v1 net001 vss! pulse (vss vdd periodo 0.0002p 0.0002p periodo 'periodo*2')

vdd vdd! 0 dc=vdd

vss vss! 0 dc=vss

X50 net001 A INVREF
X51 A Q inversora
X52 Q net004 INVREF
C1 net004 vss! 0
.option acct=0 LIST ALT999 autostop=1 nomod nopage nowarn post
.tran 5p 'periodo*8' sweep vdd 1.2 0.575 -0.025
********control

.measure tran inv_1
+TRIG v(A) VAL='vdd*0.5' TD=0NS CROSS=5
+TARG v(Q) VAL='vdd*0.5' TD=0NS CROSS=5

.measure tran inv_2
+TRIG v(A) VAL='vdd*0.5' TD=0NS CROSS=6
+TARG v(Q) VAL='vdd*0.5' TD=0NS CROSS=6

*********************
.end

I obtain this results:

vdd inv_1 inv_2 temper alter#
1.200000e+000 6.592531e-012 7.355689e-012 25.000000 1
1.175000e+000 7.084245e-012 7.246606e-012 25.000000 1
1.150000e+000 7.454997e-012 7.093553e-012 25.000000 1
1.125000e+000 7.968364e-012 6.965860e-012 25.000000 1
1.100000e+000 8.175268e-012 6.823739e-012 25.000000 1
1.075000e+000 8.571015e-012 6.643237e-012 25.000000 1
1.050000e+000 8.998024e-012 6.546153e-012 25.000000 1
1.025000e+000 9.452456e-012 6.700536e-012 25.000000 1
1.000000e+000 9.905484e-012 6.425311e-012 25.000000 1
9.750000e-001 1.028735e-011 5.853116e-012 25.000000 1
9.500000e-001 1.121101e-011 5.612188e-012 25.000000 1
9.250000e-001 1.150395e-011 5.407900e-012 25.000000 1
9.000000e-001 1.223138e-011 5.278299e-012 25.000000 1
8.750000e-001 1.312154e-011 4.703371e-012 25.000000 1
8.500000e-001 1.396490e-011 4.017603e-012 25.000000 1
8.250000e-001 1.494785e-011 3.600437e-012 25.000000 1
8.000000e-001 1.582798e-011 3.190836e-012 25.000000 1
7.750000e-001 1.669294e-011 2.435148e-012 25.000000 1
7.500000e-001 1.818309e-011 2.019901e-012 25.000000 1
7.250000e-001 2.114742e-011 -2.249773e-012 25.000000 1
7.000000e-001 2.367544e-011 -3.880669e-012 25.000000 1
6.750000e-001 -1.972755e-009 -2.024577e-009 25.000000 1
6.500000e-001 -1.966810e-009 -2.027208e-009 25.000000 1
6.250000e-001 -1.958805e-009 -2.032337e-009 25.000000 1
6.000000e-001 7.206343e-011 8.899508e-011 25.000000 1
5.750000e-001 1.005491e-009 1.019330e-009 25.000000 1

But i dont understand why when the VDD is 0.675 and lower, appear negative values with the message "target time is smaller than trigger time"

How can be possible this?

thanks for your attention

 

[erikl]

How can be possible this?

Ringing, perhaps? Check the plot!