Re[2]: Ramp Def. ??

Text item:

Ahmed,

In my opinion, the IBIS spec defines the ramp rates only one way, and clearly.
See included sections below. Could you please point it out to me where you
think the other definition is in the spec?

Thanks,

Arpad Muranyi
Intel Corporation

|==============================================================================
| Keyword: [Ramp]
| Required: Yes, except for inputs and terminators
| Description: Defines the rise and fall times of a buffer. The ramp rate
| does not include packaging but does include the effects of the
| C_comp parameter.
| Sub-Params: dV/dt_r, dV/dt_f, R_load
| Usage Rules: The rise and fall time is defined as the time it takes the
| output to go from 20% to 80% of its final value.
| The ramp rate is defined as:
|
| dV 20% to 80% voltage swing
| -- = ----------------------------------------
| dt Time it takes to swing the above voltage
|
| The ramp rate must be specified as an explicit fraction
| and must not be reduced. The [Ramp] values can use "NA" for
| the min and max values only. The R_load subparameter is
| optional if the preferred 50 ohm load is used. The R_load sub-
| parameter is required if a non-standard load is used.
|==============================================================================
|
| NOTES ON DATA DERIVATION METHOD
|
|
| 3) Ramp Rates:
|
| c. Due to the resistor, output swings will not make a full transition as
| expected. However the pertinent data can still be collected as
| follows:
| 1) determine the 20% to 80% voltages of the 50 ohm swing
| 2) measure this voltage change as "dV"
| 3) measure the amount of time required to make this swing "dt"
|

===============================================================================
Hello Bob and Stephen

     Thank you for your responses. Your answers are what I expected.
However, the IBIS specifications are not clear on that. In fact it defines
ramp rate in both ways. So we should make correction on the specifications.

Regards, Ahmed.

>>>> Bob Ross wrote:

Ahmed:

Case (b).

The 20% and 80% voltage points are 1.8 V and 4.2 V.

Best Regards,
Bob Ross
Interconnectix, Inc.

>>>> Stephen Peters wrote:

Hello Ahmed:

   It's the 20% to 80% of the voltage swing. Specifically
the Dt number is calculated as (for rising wavefront)....

(time at which voltage waveform crosses [.8(voltage swing) +
starting voltage]) - (time at which voltage waveform crosses
[.2(voltage swing) + starting voltage]).

         Hope that helps.

           Regards,
           Stephen Peters
           Intel Corp.

>>>> Ahmed Omer wrote:

Hello IBIS people

Is ramp rate defined as the time it takes the output to go:
(a) 20% to 80% of output final value
 or
(b) 20% to 80% of output voltage swing*

* I define voltage swing as the difference
  between final value and initial value.

For example;
Say, the output swings 1 to 5 volts. | 5 v ____
To calculate the ramp rate do I use | /
(a) 20% to 80% of 5 volts | /
 or | /
(b) 20% to 80% of 4 volts | 1v ____/

Regards, Ahmed.
|---------------------------------------+------------------------------------|
|Ahmed Omer | Advanced Interconnect Systems Labs |
|E-MAIL: omera@trailblazer.sps.mot.com | Semiconductor Products Sector |
| : R28450@email.sps.mot.com | M O T O R O L A, Inc. |
|Phone: 512-933-2247 | 3501 Ed Bluestein Blvd MDrop: F36
 |
|Fax: 512-933-5845 | Austin, TX 78721 |

|____________________________________________________________________________|

Text item: External Message Header

The following mail header is for administrative use
and may be ignored unless there are problems.

***IF THERE ARE PROBLEMS SAVE THESE HEADERS***.

X-Sun-Charset: US-ASCII
Subject: Re: Ramp Def. ??
To: ibis@vhdl.org
Message-Id: <9610241438.AA02524@trailblazer.aisl.aus>
From: omera@trailblazer.sps.mot.com (Ahmed Omer)
Date: Thu, 24 Oct 1996 09:38:40 -0500
Received: by trailblazer.aisl.aus (5.x/SMI-SVR4)
     id AA02524; Thu, 24 Oct 1996 09:38:40 -0500
Received: from emailmesa (emailmesa.sps.mot.com) by mogate.sps.mot.com (4.1/SMI-
4.1/Email-2.0)
     id AA28890 for ibis@vhdl.org; Thu, 24 Oct 96 07:37:42 MST
Received: from mogate.sps.mot.com by spsgate.sps.mot.com (4.1/SMI-4.1/Email 2.1
10/25/93)
     id AA27429 for ibis@vhdl.org; Thu, 24 Oct 96 07:37:47 MST
Received: from spsgate.sps.mot.com (spsgate.sps.mot.com [192.70.231.1]) by vhdl.
vhdl.org (8.7.3/8.7.3) with SMTP id HAA29154 for <ibis@vhdl.org>; Thu, 24 Oct 19
96 07:48:37 -0700 (PDT)
Received: from vhdl.vhdl.org (vhdl.vhdl.org [198.31.14.3]) by ormail.intel.com (
8.7.6/8.7.3) with ESMTP id HAA05439; Thu, 24 Oct 1996 07:45:44 -0700 (PDT)
Received: from ormail.intel.com (ormail.intel.com [134.134.248.3]) by relay.jf.i
ntel.com (8.7.4/8.7.3) with ESMTP id HAA21430; Thu, 24 Oct 1996 07:45:43 -0700 (
PDT)
Return-Path: owner-ibis@vhdl.vhdl.org
Received on Tue Oct 29 11:01:02 1996