It was brought to my attention that the [Model Spec] keyword does not
specify whether the subparameters are required or not. The question is,
can we use some of them but not others, or once the keyword is specified,
do all of the subparameters have to be present?
Arpad
=========================================================================
-----Original Message-----
From: Bob Ross [mailto:bob_ross@mentorg.com]
Sent: Tuesday, August 03, 1999 10:58 AM
To: ibis@eda.org
Cc: bob_ross@mentorg.com
Subject: IBIS BIRD59 MODEL SPEC DIAGRAMS
To IBIS Committee:
BIRD59 documents the intended diagrams to be included in IBIS Version 3.2
in response to editorial letter ballot comments on SP-4557 for more
clarification.
Please review these for discussion at the Friday August 6, 1999 IBIS
Meeting.
Bob Ross
Mentor Graphics
****************************************************************************
**
****************************************************************************
**
BIRD ID#: 59
ISSUE TITLE: Model Spec Diagrams
REQUESTER: Bob Ross, Mentor Graphics
DATE SUBMITTED: August, 1999
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
****************************************************************************
**
****************************************************************************
**
STATEMENT OF THE ISSUE:
The need to illustrate some [Model Spec] subparameters was raised in letter
ballot responses to SP-4557.
****************************************************************************
**
STATEMENT OF THE RESOLVED SPECIFICATIONS:
The [Model Spec] keyword is presented with added diagrams. Also the |*
adds a clarifying remark concerning the static overshoot definition.
Replace the existing [Model Spec] keyword with the text below:
|===========================================================================
==
| Keyword: [Model Spec]
| Required: No
| Sub-Params: Vinh, Vinl, Vinh+, Vinh-, Vinl+, Vinl-, S_overshoot_high,
| S_overshoot_low, D_overshoot_high, D_overshoot_low,
| D_overshoot_time, Pulse_high, Pulse_low, Pulse_time, Vmeas
| Description: The [Model Spec] keyword defines four columns under which
| specification subparameters are defined.
|
| The following subparameters are defined:
| Vinh Input voltage threshold high
| Vinl Input voltage threshold low
| Vinh+ Hysteresis threshold high max Vt+
| Vinh- Hysteresis threshold high min Vt+
| Vinl+ Hysteresis threshold low max Vt-
| Vinl- Hysteresis threshold low min Vt-
| S_overshoot_high Static overshoot high voltage
| S_overshoot_low Static overshoot low voltage
| D_overshoot_high Dynamic overshoot high voltage
| D_overshoot_low Dynamic overshoot low voltage
| D_overshoot_time Dynamic overshoot time
| Pulse_high Pulse immunity high voltage
| Pulse_low Pulse immunity low voltage
| Pulse_time Pulse immunity time
| Vmeas Measurement voltage for timing
measurements
|
| Usage Rules: [Model Spec] must follow all other subparameters under the
| [Model] keyword.
|
| For each subparameter contained in the first column, the
| remaining three hold its typical, minimum and maximum
values.
| The entries of typical, minimum and maximum must be placed
on
| a single line and must be separated by at least one white
| space or tab character. All four columns are required under
| the [Model Spec] keyword. However, data is required only in
| the typical column. If minimum and/or maximum values are
not
| available, the reserved word "NA" must be used indicating
the
| typical value by default.
|
| The minimum and maximum values are used for specifications
| subparameter values that may track the min and max operation
| conditions of the [Model]. Usually it is related to the
| Voltage Range settings.
|
| Unless noted below, each subparameter does not require
having
| any other subparameter.
|
| Vinh, Vinl rules:
|
| The threshold subparameter lines provide additional min and
| max column values, if needed. The typ column values are
still
| required and would be expected to override the Vinh and Vinl
| subparameter values specified elsewhere. Note: the syntax
| rule that require inserting Vinh and Vinl under models
remains
| unchanged even if the values are defined under the [Model
| Spec] keyword.
|
| To mimic a hysteresis effect, the values of Vinh and Vinl
may
| be interchanged such that the Vinl value is larger than the
| Vinh value. However, simulators may process this
information
| differently or report an error.
|
| Vinh+, Vinh-, Vinl+, Vinl- rules:
|
| The four hysteresis subparmeters must all be defined before
| the hysteresis threshold rules become effective. Otherwise
| the standard threshold subparameters remain in effect. The
| hysteresis thresholds shall be at the Vinh+ and Vinh- values
| for a low-to-high transition, and at the Vinl+ and Vinl-
| values for a high-to-low transition.
|
| |
| | Receiver Voltage with Hysteresis Thresholds
| |
| |
| | oo o
| | o oo ooooooooo
| | o o
| Vinh+ | - - - - - - - - - x o
| Vinh- | - - - - - - - - x o
| | o o
| | o o
| | o o
| Vinl+ | - - - - - - o - - - - - - - - - - - - - - - - - x
| Vinl- | - - - - - - o - - - - - - - - - - - - - - - - - x
| | o o
| | o o
|
|oooooo-----------------------------------------------------oooooooo
|
| Time -->
|
| S_overshoot_high, S_overshoot_low rules:
|
| The static overshoot subparameters provide the voltage
values
| for which the model is no longer guaranteed to function
|* correctly. Typically these are voltages which would cause
|* the physical component to be destroyed.
|
| D_overshoot_high, D_overshoot_low, D_overshoot_time rules:
|
| The dynamic overshoot values provide a time window during
| which the overshoot may exceed the static overshoot limits
| but be below the dynamic overshoot limits. D_overshoot_time
| is required for dynamic overshoot testing. In addition, if
| D_overshoot_high is specified, then S_overshoot_high is
| necessary for testing beyond the static limit. Similarly,
if
| D_overshoot_low is specified, then S_overshoot_low is
| necessary for testing beyond the static limit.
|
| |
| | Receiver Voltage with Static and Dynamic Overshoot Limits
| |
| |
| | D_overshoot_time ->| |<-
| | | |
| D_overshoot_high - - - - - - -+ - - -+
| | | oo | Passes - Does Not Exceed Bounds
| | |o o |
| S_overshoot_high - - - - - - -x o +- - - - - - - - - - - - - - - - - -
-
| | o o ooooooooo
| | o o o
| | o o
| | o o
| | o o
| | o o
| | o o
| | o o Fails -
| | o o Exceeds Bounds
| | o o | | |
| | o o V V V
|
|oooooo-------------------------------------------o---------o---oooo
| S_overshoot_low - - - - - - - - - - - - - - - - - - - - - x +x x x -
-
| | |o x x
| | | o o|
| D_overshoot_low - - - - - - - - - - - - - - - - - - - - - + -x x-+
| | | x |
| D_overshoot_time ->| |<-
|
| Time -->
|
| Pulse_high, Pulse_low, Pulse_time rules:
|
| The pulse immunity values provide a time window during which
| a rising pulse may exceed the nearest threshold value but
| be below the pulse voltage value and still not cause the
| input to switch. Pulse_time is required for pulse immunity
| testing. A rising response is tested only if Pulse_high is
| specified. Similarly, a falling response is tested only if
| Pulse_low is specified. The rising response may exceed the
| Vinl value, but remain below the Pulse_high value.
|
| Similarly, the falling response may drop below the Vinh
value,
| but remain above the Pulse_low value. In either case the
| input is regarded as immune to switching if the responses
| are within these extended windows. If the hysteresis
| thresholds are defined, then the rising response shall use
| Vinh- as the reference voltage, and the falling response
shall
| use Vinl+ as the reference voltage.
|
| |
| | Receiver Voltage with Pulse Immunity Thresholds
| |
| |
| | Switching No Switching
| | | |
| | | oo o | Switching
| | | o oo ooooooooo | |
| | | o o | |
| | V o o V oooV
| Vinh - - - - - - - - - - x - - - - - - - - - - - - - x o + -x
| | Pulse_time ->| o |<- |ooo | o
| Pulse_high - - - - - + o - + Pulse_low - + - - + o
| | |o | Pulse_time ->| |<- o
| Vinl - - - - - - - - x + - - - - - - - - - - - - - - - - - - x
| | o o
| | o o
| | o o
|
|oooooo------------------------------------------------------------o
|
| Time -->
|
| Vmeas rules:
|
| The Vmeas values under the [Model Spec] keyword override the
| Vmeas entry elsewhere.
|---------------------------------------------------------------------------
-- [Model Spec] | Subparameter typ min max | | Thresholds | Vinh 3.5 3.15 3.85 | 70% of Vcc Vinl 1.5 1.35 1.65 | 30% of Vcc | | Vinh 3.835 3.335 4.335 | Offset from Vcc | Vinl 3.525 3.025 4.025 | for PECL | | Hysteresis | Vinh+ 2.0 NA NA | Overrides the Vinh- 1.6 NA NA | thresholds Vinl+ 1.1 NA NA Vinl- 0.6 NA NA | All 4 are required | | Overshoot | S_overshoot_high 5.5 5.0 6.0 | Static overshoot S_overshoot_low -0.5 NA NA D_overshoot_high 6.0 5.5 6.5 | Dynamic overshoot D_overshoot_low -1.0 -1.0 -1.0 | requires | | D_overshoot_time D_overshoot_time 20n 20n 20n | & static overshoot | | Pulse Immunity | Pulse_high 3V NA NA | Pulse immunity Pulse_low 0 NA NA | requires Pulse_time 3n NA NA | Pulse_time | | Timing Thresholds | Vmeas 3.68 3.18 4.68 | A 5 volt PECL | | example | |=========================================================================== == **************************************************************************** ** ANALYSIS PATH/DATA THAT LED TO SPECIFICATION: Diagrams are added to clarify meanings and also to illustrate switching points for the Vinl-, Vinl+, Vinh-, and Vinh+ hysteresis subparameters and for the pulse immunity subparameters Pulse_high, Pulse_low, and Pulse_time. Diagrams also show regions where the receiver waveform passes and fails the overshoot constraints based on S_overshoot_high, S_overshoot_low, D_overshoot_high, D_overshoot_low, and D_overshoot_time subparameters. A short explaination is added for the static overshoot parameters to respond to Intel's comment below. **************************************************************************** ** ANY OTHER BACKGROUND INFORMATION: This is in response to two letter ballot comments submitted in June, 1999 on SP-4557 for EIA ratification of Version 3.2 from Cisco Systems and Intel. The comments are shown below: Cisco Systems Comment 1 was: Cisco Systems: 1 Editorial Reference: Page 24 Suggested Change: Add a hysteresis diagram showing all the sub-parameters. Rationale: Would clarifiy usage of Vinh+, Vinh-, Vinl+, Vinl-, S_overshoot_high, S_overshoot_low, D_overshoot_high, D_overshoot_low, D_overshoot_time, Pulse_high, Pulse_low, Pulse_time. Intel: 7 Editorial Reference: Page 24 Suggested Change: the whole discussion on dynamic and static overshoot is confusing. I can't figure out if static or dynamic overshoot implies an absolute maximum rating or device destruction or what. Not sure how to fix, but this does need to be clarified. **************************************************************************** **Received on Tue Aug 3 12:30:17 1999
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