Re: Question about Re: Serious s2ibis problem?

Hello Scott,

Thank you for your response.
I have been using s2ibis2 version 0.91BETA in this 6 months
and have developed about more than 10 IBIS models for memory device.
Is it the latest version of s2ibis2 ?
Is this version of s2ibis2 different from yours ?

My setting of .s2i command file for s2ibis2 shows below.
(DQ-buffer is 3-state type IN/OUT(bi-directional) buffer.)

( .s2i command file)
<snip>
---------------------------------------------
[Pin]
|pin_name spice_node signal_name model_name
1 23 DOUT DQ_BUF
-> input ena
2 2 VDD POWER
3 0 GND GND
input 15 DATA DUMMY1
ena 9 ENABLE DUMMY1
|
|
[Model] DQ_BUF
[Model type] 3-state
[Polarity] Non-Inverting
[Enable] Active-High
------------------------------------------------
<snip>

Here,when ENABLE is Active-High,I modify my SPICE netlist
(.sp file) to tie ENABLE pin thru a resistor(10Kohm and so on) to GND.
(It means to set the buffer to be disable.)

GND ----- resistor -----ENABLE ----> (to DQ-buffer control)

Because,though s2ibis2 set voltage to ena pin for pullup/pulldown
(for example,VENAS2I 21 0 DC 0),it does not set for output disable .spi files
(for example, ddnout1.spi, ddtout1.spi and ddxout1.spi).
I wonder why s2ibis2 does not set voltage for output disable simulation
automatically.

Then I was able to get the normal end of s2ibis2 program.
And It seem s2ibis2 generate a good Pulldown/Pullup tables according to
IBIS V2.1 spec.,if my assumptions are right.

If you have any other informations concerning s2ibis2 algorythm ,
please let me know. Thank you.

And I insert my another comments below.

(P.S.)I don't receive NCSU or IBIS FORUM response yet,
      though I understand NCSU peoples are busy.
      I hope that IBIS OPEN FORUM ask some EDA vendor to support
      and update a s2ibis2 program as well as IBIS simulators.

Best Regards,
Midori Nakamae
Mitsubishi Electric Corp. JAPAN

At 10:32 AM 96.11.11 -0800, Scott Schlachter wrote:
>Nakamae,
>
>I have also been using s2ibis to generate IBIS files, and I have talked
>to many people about the algorythm that it uses to generate the
>tables. Your assumptions apear to be correct, including what you asked
>about how the simulators sum the clamp curve data to the pull-up and
>pull-down data when the output buffer is active (non-tristate). If you
>are using s2ibis (not s2ibis2), then you can also read about the
>algorythm that s2ibis uses in the FAQ file, under the /src directory
>that gets created when you untar the s2ibis program.
>
>As for how s2ibis deals with you n-channel pull-up, it really sounds
>like it is not set up correctly. You should be getting big values
>in your power-clamp curve - and you are getting zeros! s2ibis performs
>no subtraction to the power-clamp data that it gets from the spice run
>that it performs. It records this data directly to the [Power-clamp]
>table in the created .ibs file (after it shifts all of the voltage
>values to represent the Vtable = Vcc - Vout requirement).
>
>If you want to see exactly what the signals are for the Power-clamp (and
>what the spice file looks like), look under the file pc<pin-name>.spi,
>and the corresponding pc<pin-name>.out output file. For example,
>if your pin-name is "One", than the files would be pcOne.spi, and
>pcOne.out . These files will only be left behind if you DON'T have the
>*[Cleanup] command in your s2ibis input file!
>

Yes,I know. Thanks.

>I would start by examining the FAQ and also the pc---.spi files. If you
>don't have the FAQ, let me know and I can email it to you. There has
>been a lot of discussion lately in the IBIS community that we should not
>bother the people at NCSU too much about the s2ibis programs, as 1) they
>provided them for free to the IBIS community, 2) they don't really
>have the money or man-power to support the programs (and they never
>said they would support them), and finally 3) Alan Glaser and others
>there are busy trying to finalize the s2ibis2 program with what little
>amount of funds they have.

Yes,I understand.

>
>Hope this helps,
>-Scott Schlachter
> Design Engineering
> Actel Corporation
>
Received on Tue Nov 12 03:56:50 1996