Help with spectre stimulus file for sram read.

[rajrevanth61]

Hello Experts,

I have a spectre stimulus file for SRAM read operation , but when i include the file and simulate via the spectre, I am not getting the expected results, can anyone check if my stimulus file is correct or not.

simulator lang=spectre
global gnd!
vdd (vdd! 0) vsource dc=1
gnd (gnd! 0) vsource dc=0
ic Q=1 Qb=0 BL=1 BLB=1
v6 (WL 0) vsource type=pwl wave=[0 0 20n 0 22n 1 40n 1v 42n 0v]

This is the schematic. I have initialized the conditions required for the read operation . i.e., I want to read a value of 1 so i have initialized Q as 1 and QR as 0. and for the read operation to take place both the bitlines have been initialized to 1. I have used PWL as the source for the word line(WL).
These are the warnings I am getting when i try to simulate. are these warnings causing my output to be improper?

Notice from spectre during topology check.
Only one connection to the following 2 nodes:
BL
BLB
No DC path from node `WL' to ground, Gmin installed to provide path.
Warning from spectre during heuristic topology check - set topcheck=fixall to fix all floating nodes.
WARNING (SPECTRE-7): No DC path from node `vdd!' to ground.
WARNING (SPECTRE-7): No DC path from node `gnd!' to ground.

 

[dick_freebird]

I think maybe you want those supplies and stimulus sources
in the circuit, since that's how you are choosing to declare
them (as elements, not statements). They seem to be not
getting found, as is. You might want to look at the spectre
final input file (I forget which but there is a series of them in
the run directory which is the ready-to-go complete netlist,
not what "display netlist" shows you in ADE). If your sources
are not showing up there then maybe you're talking to the
wrong end of the elephant.

 

[rajrevanth61]

Hi thanks for the reply,
When I try to simulate the above circuit using the initial conditions(ADE->Simulation->Convergence Aids->Initial Condition) and sources directly in the circuit. i am getting the output correctly.

But i when i try to simulate it through the stimulus file, I am not getting the required output.
Is this stimulus file correct?
simulator lang=spectre
global gnd!
vdd (vdd! 0) vsource dc=1
gnd (gnd! 0) vsource dc=0
ic Q=1 Qb=0 BL=1 BLB=1
v6 (WL 0) vsource type=pwl wave=[0 0 20n 0 22n 1 40n 1v 42n 0v]

 

[erikl]

I think your SPECTRE syntax isn't correct: vsources need to start with "V", and may be the global node names aren't understood, as your schematic uses designations without the "!" (or the global vdd! statement is missing). So try:

[B]V[/B]vdd (vdd 0) vsource dc=1
[B]V[/B]gnd (gnd 0) vsource dc=0