[SI-LIST] Re: Creating Pseudo Random Bit Sequence (PRBS) stimuli for Hspice
- From: "Beal, Weston" <weston_beal@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 25 Nov 2002 15:58:15 -0800
Ray and Bob,
Actually, I have already fixed this little problem and send the fix to the
people who noticed it first. I just forgot to update the utility on the mentor
FTP server. I'll send you the updated utility in a private email. If anyone
else wants a copy just send me a private email and I'll send it directly to
you. The zip file is only 32KB.
Also, we shouldn't refer to this as a Mentor utility. I did this on my own
time at home and Mentor Graphics does not own, sell, nor support the utility.
It is fully my responsibility. It is simply the Pulse Train Generator (pt-gen)
from Weston.
By the way, does anyone want this to write MDC format for use in XTK?
Regards,
Weston
-----Original Message-----
From: Ray Anderson [mailto:Raymond.Anderson@xxxxxxx]
Sent: Monday, November 25, 2002 2:29 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Creating Pseudo Random Bit Sequence (PRBS)
stimuli for Hspice
>
>
>Hi! I used the utility written by Mentor(java utility)
>to create a PWL source for PRBS -10 pattern. I copied
>the PWL in my main circuit but when I run the sim it
>gives me error: "piecewise source 0:v_1a1 not
>increasing in time"
>Can somebody help me as to where I am making a
>mistake?
>The PWL source statement is:
>V_1a1 x_1a1 0 PWL (.......)
>Thanks in advance.
>Bob
I ran the Mentor utility to create a PRBS7 pattern
(127 bits long with 5ns bits) and included it in a simple
Hspice deck. It ran fine. (sample deck at end of this message).
Then I created a PRBS10 pattern as you did and attempted to run
it. I saw the same error message.
Troubleshooting shows that the problem is the commas embedded in the
time values > 1000ns. Hspice interprets the commas the same as a space.
So the spice snippet "1,000n 1.0 1,000.001n 1.0" parses out as:
1 000n 1.0 1 000.001n 1.0 . This creates the "not increasing in time"
error since .001n is < 1.0 which makes time march backwards (not a nice
thing in Hspice land).
Sounds like the author (Weston Beal) needs to make a minor tweek to the code
to make it work reliably for Hspice syntax. Perhaps the commas are Ok
in other simulators ??
-Ray Anderson
Sun Microsystems
------------------sample spice deck follows--------------------
Test Circuit to Illustrate PWL Use
R1 1 2 50 * Rseries
L 2 3 60p *
C 3 0 5p *
R 3 0 50 * Rload
* PRBS7 127 bit pattern generated by Java Utility
V1 1 0 PWL( 0.0n 1.0
+ 10n 1.0 10.001n 0.0 15n 0.0 15.001n 1.0 30n 1.0 30.001n 0.0
+ 35n 0.0 35.001n 1.0 40n 1.0 40.001n 0.0 50n 0.0 50.001n 1.0
+ 55n 1.0 55.001n 0.0 60n 0.0 60.001n 1.0 70n 1.0 70.001n 0.0
+ 85n 0.0 85.001n 1.0 95n 1.0 95.001n 0.0 100n 0.0 100.001n 1.0
+ 120n 1.0 120.001n 0.0 125n 0.0 125.001n 1.0 135n 1.0 135.001n 0.0
+ 140n 0.0 140.001n 1.0 145n 1.0 145.001n 0.0 150n 0.0 150.001n 1.0
+ 160n 1.0 160.001n 0.0 165n 0.0 165.001n 1.0 175n 1.0 175.001n 0.0
+ 185n 0.0 185.001n 1.0 190n 1.0 190.001n 0.0 200n 0.0 200.001n 1.0
+ 205n 1.0 205.001n 0.0 220n 0.0 220.001n 1.0 235n 1.0 235.001n 0.0
+ 255n 0.0 255.001n 1.0 260n 1.0 260.001n 0.0 265n 0.0 265.001n 1.0
+ 290n 1.0 290.001n 0.0 300n 0.0 300.001n 1.0 305n 1.0 305.001n 0.0
+ 310n 0.0 310.001n 1.0 315n 1.0 315.001n 0.0 320n 0.0 320.001n 1.0
+ 335n 1.0 335.001n 0.0 345n 0.0 345.001n 1.0 355n 1.0 355.001n 0.0
+ 360n 0.0 360.001n 1.0 365n 1.0 365.001n 0.0 380n 0.0 380.001n 1.0
+ 385n 1.0 385.001n 0.0 395n 0.0 395.001n 1.0 415n 1.0 415.001n 0.0
+ 430n 0.0 430.001n 1.0 435n 1.0 435.001n 0.0 440n 0.0 440.001n 1.0
+ 445n 1.0 445.001n 0.0 465n 0.0 465.001n 1.0 475n 1.0 475.001n 0.0
+ 500n 0.0 500.001n 1.0 505n 1.0 505.001n 0.0 535n 0.0 535.001n 1.0
+ 570n 1.0 570.001n 0.0 575n 0.0 575.001n 1.0 580n 1.0 580.001n 0.0
+ 585n 0.0 585.001n 1.0 590n 1.0 590.001n 0.0 595n 0.0 595.001n 1.0
+ 600n 1.0 600.001n 0.0 610n 0.0 610.001n 1.0 620n 1.0 620.001n 0.0
+ 630n 0.0 630.001n 1.0 635n 1.0 )
.tran 1ns 650ns
.option post=1
.END
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