TOPIC : Types of Simulation

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TOPIC Types of Simulation
UNIT 1 Modeling
Module 1.5 Simulation
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Types of Simulation

• A simulator that executes a compiled code
  model(e.g. RTL) is referred to as a compiler-code
  simulator.
• A simulator that interprets a model based on data
  structure is said to be table-driven.
• Activity directed simulation is referred to as
  event-driven Simulation.

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Compiled Simulation

• Compiled simulation allows the inputs to changed
  only when the circuit is stable.
• Input vectors or stimuli are applied at a fixed
  rate.
• It is mainly oriented toward functional
  verification and is not concerned with the timing
  of the circuit.
• It evaluates all the elements in the circuit for
  every input vector.

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Example of Compiled Simulation

• The compiled-code of this circuit is
• LDA B
• AND Q
• INV
• STA E
• OR A
• STA F
• STA Q
• It will simulate for every value of A and B.

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Asynchronous circuit with compiled-code model
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Event driven Simulation

• It can process real time inputs, that is, inputs
  whose times of change are independent of the
  activity in the simulated circuits.
• It allows accurate simulation of non-synchronized
  events such as interrupts or competing requests
  for use of bus.

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Main flow of event driven Simulation
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Event-driven Simulation

• Event change in logic value at a node, at a
  certain instant of time ? (V,T)
• Event-driven only considers active nodes
• Efficient
• Performs both timing and functional verification
• All nodes are visible
• Glitches are detected
• Most heavily used and well-suited for all types
  of designs

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Event-driven Simulation

• Event change in logic value, at a certain
  instant of time ? (V,T)

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Level of Simulation

• Register level Simulation RTL
• Functional-level Simulation primitive
  functional block
• Gate level Simulation
• Transistor level Simulation
• Mixed-level Simulation

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Classification of Simulators

• HDL-based Design and testbench described using
  HDL
• Event-driven
• Cycle-based
• Schematic-based Design is entered graphically
  using a schematic editor
• Emulators Design is mapped into FPGA hardware
  for prototype simulation. Used to perform
  hardware/software co-simulation.

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Classification of Simulators
Logic Simulators
Event-driven
Cycle-based
Gate
System
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Simulation engine

• Logic simulation of complex VLSI circuits and
  systems is a time-consuming process.
• Hardware especially designed to speed-up
  simulation is called Simulation engines.
• Simulation engines achieve the speed-up based on
  two different strategies model partitioning and
  algorithm partitioning.

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Types of Simulation Engine

• Model partitioning consists of dividing the
  model of the simulated circuit into disjoint sub
  circuits, concurrently simulated by identical
  processing units (Pus), interconnected by a
  communication medium.
• Algorithm partitioning consists of dividing the
  simulation algorithm into tasks distributed among
  different Pus working concurrently as stages of a
  pipeline.