Subject: BIRD50.2 - Add Model Bus Hols

From: [email-masked] (Bob Ross)
Date: Fri, 29 May 98 10:52:57 PDT

Dear IBIS Folks:

BIRD50 describes a bus hold extension which is also useful for other similar
structures.

BIRD50.1 is issued with these changes: 

  The title is corrected.
  [Add Model Spec] is required for bus hold models
  Add_model_mode is illustrated
  Any other minor editorial correction

Changes occurred or are documemented in the |* lines.

The only change in BIRD50.2 is to delete the Add_model_mode subparameter
in the example since BIRD48.3 deletes this subparameter.

Bob Ross
Interconnectix/Mentor Graphics

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BIRD ID#:       50.2
ISSUE TITLE:    Add Model Bus Hold
REQUESTER:      Neven Orhanovic, Bob Ross, Mentor G., Arpad Muranyi, Intel
DATE SUBMITTED: 4/2/98, 5/21/98, 5/29/98
DATE ACCEPTED BY IBIS OPEN FORUM: Pending

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STATEMENT OF THE ISSUE:

New devices incorporate bus hold or other latching mechanisms to hold the
input at a particular state using some active pullup and pulldown components.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

The Bus Hold functionality is added in the new Section 6a:

| Bus Hold:
|
|* When the Model_type subparameter under the [Model] keyword is set to
|* Bus_hold, the added model describes the bus hold functionality.  This
|* section introduces the dynamic clamp add model functionality.
|
|* Existing keywords and subparameters are used to describe bus hold models.
|* The [Pullup] and [Pulldown] tables both are used to define a weak internal 
|* buffer that is triggered switch to its opposite state.  This switching
|* transition is specified by a [Ramp] keyword or by the [Rising Waveform]
|* and [Falling Waveform] keywords.
|*
|* For bus hold models, the [Add Model Spec] and V_trigger_r and V_trigger_f
|* subparameters are required.
|
| The transition is triggered by action at the die using the [Add Model Spec]
| V_trigger_r and V_trigger_f subparameters as follows:
|
|* If the starting voltage is below V_trigger_f, then the bus_hold model is
|* set to the low state causing additional pulldown current.  If the starting
|* voltage is above V_trigger_r, the bus hold model is set to the high
| state for additional pullup current.  When the input passes though
| V_trigger_f during a high-to-low transition at the die, the bus hold output
|* switches to the low state.  Similarly, when the input passes though
|* V_trigger_r during a low-to_high transition at the die, the bus hold output
|* switches to the high state.
|
| No additional keywords are needed for this functionality.

|------------------------------------------------------------------------------
|
| Complete Bus_hold Model Example:
|
[Model]       Bus_hold_1
Model_type    Bus_hold
C_comp        0 0 0
|
[Add Model Spec]
|   Subparameter          typ        min        max
|
V_trigger_f               1.3        1.2        1.4  | Falling edge trigger
V_trigger_r               3.1        2.6        4.6  | Rising edge trigger
|
[Pulldown]   
|
-5V     -100uA     -80uA     -120uA
-1V      -30uA     -25uA     -40uA
0V       0           0         0
1V       30uA       25uA     40uA
3V       50uA       45uA     50uA
5V       100uA      80uA     120uA
10v      120uA      90uA    150uA
|
[Pullup]
|
-5V      100uA      80uA     120uA
-1V      30uA       25uA     40uA
0V       0           0         0
1V       -30uA      -25uA    -40uA
3V       -50uA      -45uA    -50uA
5V       -100uA     -80uA    -120uA
10v      -120uA     -90uA    -150uA
|
|****************************************************************************
|
[Ramp]
|                       typ             min             max
dV/dt_r                 2.0/0.50n       2.0/0.75n       2.0/0.35n
dV/dt_f                 2.0/0.50n       2.0/0.75n       2.0/0.35nn
|
|****************************************************************************

|==============================================================================

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

A weak driver can be added using the [Add Model] keyword.

BIRD50.1 adds the statement that [Add Model Spec] and its V_trigger_r and
V_trigger_f subparameters are required.  This is because [Add Model Spec]
may not be required for other added models.

BIRD50.2 deletes the Add_model_mode subparameter in the example since
BIRD48.3 deletes this subparameter.

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ANY OTHER BACKGROUND INFORMATION:

This proposal is based on a conversation with Bob Ross, Chris Reid, and
Arpad Muranyi on March 11, 1998.

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