Re: Questions about Submodels

So regarding data extraction, are the following statements correct?

To get the clamp curves of the top-level model, the bus-hold
feedback has to be removed from the input.

Then in the submodel:

For V_trigger:
 With the bus-hold output connected to the input, sweep the
 input voltage from low-to-high, and then from high to low and
 monitor the current at the voltage source. Where the bi-stable
 flip-flop (bus-hold circuit) transitions from opposing current
 to aiding current (passes through zero) is the V_trigger point.

For Pulldown:
 With the bus-hold output disconnected from the input,
 hold the input low, so that the bus-hold output node is low,
 and sweep the V/I curve of the bus-hold output.
 Or alternatively, you may be able to hold the input of the
 bus-hold driver high (inverter) and the bus-hold output will
 go low. Then sweep the output VI curve.

For Pullup:
 With the bus-hold output disconnected from the input,
 hold the input high, so that the bus-hold output node is high,
 and sweep the V/I curve of the bus-hold output.
 Or alternatively, you may be able to hold the input of the
 bus-hold driver low (inverter) and the bus-hold output will
 go high. Then sweep the output VI curve.

For Ramp:
 With the bus-hold output disconnected from the input,
 and a load capacitance connected to the output of the bus-hold
 to simulate the load of the input, ramp the input to read the
 dV/dt output edge-rates at the output of the bus-hold.
 Or alternatively, you could leave the bus-hold all hooked up and
 provide the input stimulus at the input of the bus-hold driver stage.

For reference, assuming a buffer device ('244) with bus hold, the input stage
looks like this:

       Bus-hold output /|
               +------o/ |----+
               | \ | |
               | \| |
               | |\ |
PIN O----------+-----| \o-----+----------->off to rest of circuitry
      Device input | / Input inverter/buffer
                     |/

-- 
Regards,
Stephen M. Nolan
Bob Ross wrote:
> 
> Stephen:
> 
> My responses are in your text.
> 
> Bob Ross
> Mentor Graphics
> 
> Stephen Nolan wrote:
> >
> > Hi IBIS folks. I'm working on our procedures for creating IBIS models of devices
> > with Bus Hold, and struggling through this section 6a on Submodels. Help.
> >
> > First of all, are submodels a section that is entirely contained within a model
> > section, or are they independant and inheritable by other models? For example,
> > if I have an input model:
> >
> > |******************************************************************************
> > [Model]             LVTH244_DATAIN_33
> > Model_type          Input
> > Vinl = 0.8V
> > Vinh = 2.0V
> > C_comp              3.35pF       NA           NA
> > |
> > [Add Submodel]
> > BUS_HOLD_33         Non-Driving
> > |
> > |******************************************************************************
> >
> > Does the submodel BUS_HOLD_33 have to follow the data in the LVTH244_DATAIN_33
> > model and be within that model, or can all of the submodels be at the end of a
> > file in a separate section following the models?
> 
> It can be in a separate section.
> 
> >
> > Further, once I have declared a "[Submodel] BUS_HOLD_33" submodel within the
> > LVTH244_DATA_IN_33 model, do I have to include the complete submodel again
> > within the LVTH244_OE_IN_33 model, or can I just simply call it and expect the
> > simulator to use it. If submodels do in fact turn out to be local instead of
> > global and inheritable, is there any namespace conflict?
> 
> They are global, so there is no namespace conflict.
> 
> >
> > Next is the question of data extraction for bus-hold. The clamp curves in the
> > main model contain all of the data on the VI characteristics of the bus
> > hold-circuitry. See the attached pdf file for an example. What is the purpose of
> > the trigger and pullup/down data in the submodel section? What information does
> > it provide that is not already available in the clamp curves of the main model?
> > How do you extract the Ramp data (test setup).
> 
> The clamp information is in addition to the bus hold operation.  The clamp
> tables should have 0 current in the normal operating regions (between 0 and
> Vcc).
> The Bus Hold circuitry which are really weak, triggered flip-flops are what
> the submodel models.  The advantage of the submodel approach is that the
> dynamic effects of the Bus Hold circuit are simulated.  The clamp approach
> would capture only a static (DC) characteristic and assume instantenous
> Bus Hold Operation.
> 
> The Bus_hold operation can also be used for dynamic terminations.  That is
> the main motivation for adding this to IBIS.
> 
> >
> > Finally, in the spec there is the following sentence:
> > > | The [Pullup] and [Pulldown] tables both are used to define an internal
> > > | buffer that is triggered switch to its opposite state.
> > What does this mean and is this sentence grammatically correct? I can't figure
> > it out.
> 
> It should read:
> | The [Pullup] and [Pulldown] tables both are used to define an internal
> | buffer that is triggered "to" switch to its opposite state.
> 
> >
> > Thanks.
> > --
> > Regards,
> > Stephen M. Nolan
> >
> >   --------------------------------------------------------------------------------
> >                         Name: busholdcurves.pdf
> >    busholdcurves.pdf    Type: Portable Document Format (application/pdf)
> >                     Encoding: base64