RAIL Revision Or Apendage Document  (ROAD)

ROAD ID#:      5
ISSUE TITLE:   Clarification of Overshoot Specification 
REQUESTOR:     John Keifer, Intel Corporation
DATE SUBMITTED:                       January 21, 1997
DATE ACCEPTED BY RAIL WORKGROUP:      January 23, 1997

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STATEMENT OF THE ISSUE:

The RAIL overshoot specification should be described as an absolute maximum
overshoot spec that could be used as a net or class design rule or goal.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

Change Other Notes Notes under the [Budgets] section to read the 
following:

|              MAXIMUM OVERSHOOT HIGH - This parameter specifies an absolute
|              maximum allowable overshoot that could be used as a net or class
|              design rule and should be applied to the receiver's input
|              after a transition to a higher voltage level.  EDA software
|              should flag an error if the simulated voltage at the
|              receiver(s) becomes higher than the voltage stated.
|
|              MAXIMUM OVERSHOOT LOW - This parameter specifies an absolute
|              maximum allowable overshoot that could be used as a net or class
|              design rule and should be applied to the receiver's input
|              after a transition to a lower voltage level.  EDA software
|              should flag an error if the simulated voltage at the
|              receiver(s) becomes lower than the voltage stated.


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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

The Version 1.1 "Other Notes" under the [Budgets] section explains the
Overshoot_min and Overshoot_max as the following:

MAXIMUM OVERSHOOT HIGH - This parameter specifies the largest
allowable dynamic overshoot that should be applied to the
receiver's input after a transition to a higher voltage level.
EDA software should flag an error if the simulated voltage
at the receiver(s) becomes higher than the voltage stated.

MAXIMUM OVERSHOOT LOW - This parameter specifies the largest
allowable dynamic overshoot that should be applied to the
receiver's input after a transition to a lower voltage level.
EDA software should flag an error if the simulated voltage
at the receiver(s) becomes lower than the voltage stated.

Considering that IBIS BIRD39 covers static overshoot (usually not used 
in simulation), predevice level DC specification of overshoot, and some 
form of dynamic overshoot, the only overshoot specification not
covered but definitely needed for simulation is an absolute overshoot 
spec.  It is suggested that RAIL not include all the forms of 
overshoot that IBIS BIRD39 does in order to avoid adding extra columns
to the [Budgets] section.

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ANY OTHER BACKGROUND INFORMATION:

There is a proposal to change IBIS syntax to S_overshoot to avoid 
confusion.
Thanks to Bob Ross for his input/discussion and suggestions.

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