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
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BIRD ID#: 59
ISSUE TITLE: Model Spec Diagrams
REQUESTER: Bob Ross, Mentor Graphics
DATE SUBMITTED: August, 1999
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
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******************************************************************************
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.
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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.
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Received on Tue Aug 3 11:04:54 1999
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