Subject: RE: [IBIS-Users] RE: Vinh and Vinl definition
From: Jeremy Plunkett (jeremy@serverworks.com)
Date: Thu Jun 19 2003 - 18:41:54 PDT
Hi Weston,
actually the HSTL and SSTL specifications both indicate that timing is
measured at the VREF crossing (see note 1 under table 2.2-c in the HSTL
spec). In system simulations you may want to allow for noise on VREF by
measuring timing at the DC levels or a custom set of levels based on the
maximum expected VREF noise at the IO ring of the receiver. Measuring timing
at the AC levels would create an unnecessarily large guardband.
The purpose of the AC levels is to qualify whether an input signal has
overdriven the comparator enough to ensure that the transition is received
with accurate timing (ie acceptable propagation delay through the input
buffer).
In system simulations I measure at all 5 thresholds, which sometimes
requires adding "dummy" input buffers with no capacitance or IV curves to
capture the extra thresholds.
regards,
Jeremy
-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Beal, Weston
Sent: Thursday, June 19, 2003 4:59 PM
To: 'Eric Hsu'; Ibis-Users (E-mail)
Cc: Frank Dunlap
Subject: [IBIS-Users] RE: Vinh and Vinl definition
Eric,
If you intend to use the IBIS model for timing simulation then use the (ac)
levels. If you are going to do noise measurements then you use the (dc)
levels. For the general case I would include two sets of Vinl and Vinh with
comments defining when to use each set.
In IBIS 4.0 you can specify all 4 levels directly in the [Receiver
Thresholds] block, but I don't know of any simulation checker that
recognizes those parameters, yet.
Regards,
Weston
> -----Original Message-----
> From: Eric Hsu [mailto:ehsu@netlogicmicro.com]
> Sent: Thursday, June 19, 2003 4:43 PM
> To: Ibis-Users (E-mail)
> Cc: Frank Dunlap
> Subject: Vinh and Vinl definition
>
> Hi IBIS experts,
>
> When reading HSTL spec. of JEDEC, it define Vinh(dc) and Vinl(dc) as
Vref+/-100mV, Vinh(ac) and Vinl(ac) as Vref+/-200mV. For ibis model, which
one it suppose to be taken?
>
> Best Regards,
>
> Eric Hsu
> Interface Technologies
> NetLogic Microsystems, Inc.
> 450 National Ave.
> Mountain View, CA 94043
> 650-961-6676 x198
> This e-mail contains NetLogic Microsystems, Inc. Confidential information
>
>
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