Markus Friedrich at 14:10, 23 January 2008

2008-01-23T14:10:40Z

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Components can be modeled in an analog, digital or mixed form. Naturally these different kinds of modeling will be treated completely different by the mixed mode simulator (automatically), however the digital models will be computed faster! 

== What is an analog, digital or mixed model ==

In the simulator some primitives (basic models) are implemented. These primitives are either analog or digital (except of the AD/DA transducers). Nearly each primitive has its own modelcard type, with which the model parameters can be adapted to a specific component (see also chapter 8.1.8.1{8.1.8.1 Models in (P)SPICE and TARGET3001!}). A circuit of these primitives can be defined as a subcircuit (macro), where the subcircuit is mixed modeled, if both analog and digital primitives are used. 

== Example NOR gate ==

It can be simply modeled by a NOR primitive, where only the delay time appears as parameter, or via an analog subcircuit with two transistors. Naturally the component can possess both models ([[Simulation on different levels]]), where the designator ANALOG (DIGITAL) should be contained in the level characteristics of the analog (digital) model. 

An integrated digital controlled analog amplifier could be mixed modeled (LEVEL = MIXED...), where only the control logic is digitally modeled. 

== How to execute an analog, digital or mixed simulation ==

The mixed mode simulator works simultaneously parallel with an analog simulator and a digital simulator (event driven), their interactions are regulated from the mixed mode mechanism. An analog or digital simulation can not be instructed directly, but can only be obtained via the selection of models. The selection of analog, digital or mixed models takes place also with the level dialog ([[Simulation on different levels]]): 
A purely analogous simulation: LEVEL settings with ANALOG=NECESSARY 
A purely digital simulation: LEVEL settings with DIGITAL=NECESSARY 

== AD/DA transducer and the I/O-Modelcard ==

How are the connections between analog and digital primitives regulated? 

'''Example:''' A resistor is connected at the output of a NOR gate (digital primitive). 
'''PROBLEM:''' The NOR output can only assume digital states (LOW, HIGH), but the resistor only "works" with current and voltage.
'''TARGET:''' The mixed mode simulator automatically inserts a DA transducer, since the associated modelcard contains all necessary parameters for the transformation. 

Also, if necessary, AD transducers will be automatically inserted at digital inputs. The modelcard for a AD transducer (primitive) contains among other things the voltage ranges for the digital states (LOW, HIGH...), i.e. at which voltage a transition from LOW to HIGH should apply etc.! 

The transducers can also be inserted manually (explicitly). 

Each digital primitive uses an I/O-Modelcard, where the selection of certain AD/DA transducers (Subcircuits) is specified. TTL and CMOS components naturally have different I/O behavior, thus they use different I/O-Modelcards with adequate AD/DA transducers. 

[[category:Simulation]] [[de: Analog, Digital oder Mixed-Mode]]

Analog, digital or mixed mode - Revision history

Markus Friedrich at 14:10, 23 January 2008