RE:analog pins in IBIS - request for clarification

As I understand it, I should put "NC" as the model name in the [Pin]
section for analog pins, but I have a few follow-up questions as well
that I hope people can answer for me.

What is the difference between including the analog pin under the [Pin]
keyword, and then putting "NC" beside it,
versus omitting the pin altogether?

Also, if I specify an analog pin in the [Pin] section with "NC" what
should I put in the [Pin Mapping] section for that pin? (Incidentally,
I know which power buses power up the analog pins) For example, say I
knew that pins 5 and 9 are analog power and ground for pin 10( which is
an analog pin), would it hurt to list pins 5 and 9 as the pullup and
pulldown reference for pin 10?

What if the analog pins that I am dealing with are a set of differential
pins (+) and (-) pair, do I include them in the [Diff Pin] section as
well? even though they have no vdiff specification? and have "NC" as
their model in the [Pin] section?

Finally, this may be a really stupid question, but I feel that I don't
quite understand why IBIS doesn't handle analog pins. Could someone
please enlighten me on this matter?

Again, your help is much appreciated,

Roland Chang

******************************************
Roland Chang ext. 2647

PMC-Sierra
Applications Department
105-8555 Baxter Place
Burnaby, BC
V5A 4V7
Tel: (604) 415-6000

email: chang@pmc-sierra.bc.ca
******************************************
>-----Original Message-----
>From: Andy Ingraham [SMTP:ingraham@wrksys.ENET.dec.com]
>Sent: June 15, 1997 2:44 PM
>To: Roland Chang; Roland Chang; ibis-users@vhdl.org
>Cc: ibis-users@vhdl.org; ingraham@wrksys.ENET.dec.com
>Subject: RE: IBIS component generation, PECL differential inputs, analog I/O
>pins, Vmeas, Cref, Rref, Vref
>
>> > Thirdly, how are analog I/O pins treated in IBIS and s2ibis2? How would
>> > I setup an analog I/O pin in s2ibis2 and IBIS?
>>
>> Scope of IBIS is restricted to analog behaviour of Digital ICS.
>> I am not sure what you really mean by analog I/O pin ?.
>
>On a mixed-signal IC, analog pins would not have models in the IBIS
>file.
>
>It seems like one might use "NA" as the model_name under the [Pin]
>keyword, to signify that these pins have no available IBIS data.
>However, that is not allowed. Instead, use "NC". Technically
>incorrect, but it tells the IBIS parser to skip those pins.
>
>[Pin] signal_name model_name R_pin L_pin C_pin
>|
> 1 RAS0# Buffer1 200.0m 5.0nH 2.0pF
> 2 RAS1# Buffer2 209.0m NA 2.5pF
> 3 Analog_out NC
>...
>
>Regards,
>Andy Ingraham
 
Received on Mon Jun 23 14:09:24 1997