Pieter J. Mosterman
Senior Research Scientist
The MathWorks, Inc.
© 2005 The MathWorks, Inc.
Advanced Technologies to Accelerate
Mixed Signal Simulation
Agenda
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Introduction
What is Link for ModelSim?
Demo
Mixed Signal Simulation
Summary
2
What is the problem?
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“Hardware verification is itself become more challenging.
Verification times have increased with rising gate count and as
overall design complexity grows. According to a survey by Collett
International Research in 2002 only 39% of designs were bug free
at first silicon, while 60% contained logic or functional flaws. More
than 20% required 3 or more silicon spins. A Collett survey also
showed that nearly 50% of total engineering time was spent in
verification.”

Hardware/Software Co-verification by Dr. Jack Horgan
http://www.edacafe.com/magazine/index.php?newsletter=1&run_date=29-Mar-2004
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What are the pains?
1.
Time and effort to verify a design: As designs get more
complex, the test benches are an order of magnitude more
complex, and consume 40-60% of project resources.

Test bench HDL code will *not* be synthesized – i.e.,
will not be a part of the shipping product – “throwaway” code

HDL test benches need to run in HDL simulators, and
HDL simulators are *extremely* slow
2.
Time and effort to construct and maintain test benches:
For each line of HDL design code in a design, a user
typically needs 10 lines of HDL test bench code to
simulate, test, and verify that 1 line of HDL code.

Constructing a test bench in a textual language is at
least as complex as the original design itself
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Maintaining the test bench from one generation of a
design to the next is very resource-intensive
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What are the pains? Solutions?
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Engineers need to verify that ASIC/FPGA
implementations correctly match their system
specifications.
y=f(x)
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Link
Using the Link for ModelSim, these engineers can
co-simulate their MATLAB and Simulink designs
with equivalent Verilog and VHDL.
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Agenda
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
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
Introduction
What is Link for ModelSim?
Demo
Mixed Signal Simulation
Summary
6
Link for ModelSim makes system-level
hardware verification possible.
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Fast and bidirectional cosimulation interface
between MATLAB and Simulink, and
ModelSim
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Agenda
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


Introduction
What is Link for ModelSim?
Demo
Mixed Signal Simulation
Summary
8
Demo
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Live
MATLAB
Demo
Edge detection demo
– Design space exploration using floating
point
– Conversion to fixed point
– Co-simulate with HDL
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Link for ModelSim allows engineers to
share models instead of I/O vectors.
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The HDL is verified in the context of an entire
system and not just as a stand-alone
component.
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System performance metrics, e.g. PER, BER,
S/N ratio can be measured.
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Agenda
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


Introduction
What is Link for ModelSim?
Demo
Mixed Signal Simulation
Summary
11
Hybrid Dynamic Systems
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Two types of behavior
– Continuous
– Discrete
An embedded controller
– Plant
•
•
–
Continuous-time
behavior
Sporadic discrete
events
Controller
•
•
Discrete-time
behavior
Frequent periodic
events
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Executing a Hybrid Dynamic System
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Integrate continuous behavior
x  f ( x, u, t )
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Discrete event behavior
– Time events
•
Pre-determined time of
occurrence
tn  nextEventTime()
–
State events
•
When a model variable
exceeds a threshold
g ( x, u , t )  0
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How to handle a discrete event
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Time-driven
– Time integrated
•
•
–
Sampled time
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•
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Integrate up till event time
Inefficient for time events
Run scheduler at lowest
rate
Inefficient for widely
spaced events
Event-driven
– Jump to event time
immediately
– Does not apply to state
events
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Where do these paradigms apply?
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Discrete event intensive models
– Controller area network (CAN) in automobiles
Many events that do not affect continuous behavior
Expensive to stop the numerical solver for each of
these
window
dc motor
current
measurement
lights controller
roof controller
window controller
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Efficiency
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Two separate solvers
– Time-driven solver
•
Numerical solver integrates time (step h)
k1  hf ( xn , yn )
h
k
k3  hf ( xn  , yn  2 )
2
2
h
k
k 2  hf ( xn  , yn  1 ) k 4  hf ( xn  h, yn  k3 )
2
2
k k
k k
yn 1  yn  1  2  3  4  O (h 5 )
6 3 3 6
•
–
Sampled time event schedule
(time up to which to integrate)
Event-driven solver
•
Event calendar
20 [ms]
open_tonneau
2020 [ms]
move_roof_up_cmd
2150 [ms]
move_down_window
2250 [ms]
stop_moving_window
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Event-driven leads
time event
state event
Continuous Time:
This sets an
event in the
event-driven
solver
This sets a
time-event
in the
time-driven
solver
This event
never occurs,
but it is
already
processed!
Scheduled Events:
Processed Events:


 

 
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Time-driven leads
This event
never occurs,
but it is
already
processed!
time event
state event
Continuous Time:
This sets a
time-event
in the
time-driven
solver
This sets an
event in the
event-driven
solver
Scheduled Events:
Processed Events:

 
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Questions
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Can we restrict the modeling constructs that are allowed?
– For example, no state events allowed to trigger events in
the event-driven solver
What inaccuracy is acceptable?
– Not do zero-crossing detection
– Run event-driven part at a quick base rate
What efficiency is necessary?
– Lock step approach
– Use one solver all together?
•
–
Other techniques?
•
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Do you lose the ability to handle a batch of discrete events
independently?
Model differently
What is the preferred configuration?
– Time-driven leads, store continuous-time state
– Event-driven leads, store discrete event state
– Alternatives?
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Agenda





Introduction
What is Link for ModelSim?
Demo
Mixed Signal Simulation
Summary
20
Summary of key features
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Integrate system level design with
implementation
No duplication of testbench design effort
Verification of system level properties
Advanced Simulation Technologies Are
Required
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