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System-On-a-Chip: A case study based on the ELIET Chip
Infineon Technologies, Sophia-Antipolis, FRANCE
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Contents


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ELIET Architecture
SoC trade-offs
Design methodology
Specification Problem
General information about ELIET
Designed to last
System Integration
Verification
Conclusion
References
Infineon Technologies, Sophia-Antipolis, FRANCE
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ELIET Architecture
 ELIET stands for Electronic ISDN Echo Canceller Transceiver
 Mixed analog/digital chip integrating all the functions required to
implement an LT (line termination) system
 ELIET building blocks are:
custom DSP
8 bit harvard micro-controller
embedded memories (ROMs and SRAMs)
different internal and external bus protocols
A/D and D/A converters
PLL
...
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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ELIET Architecture
D/A
micro code
ROMs
echo
canceller
DSP
ISDN
protocol
controller
iom/pcm arbiter
A/D
Coefficients
RAMs
filter
line
controller
framer
deframer
filter
universal external bus interface
Infineon Technologies, Sophia-Antipolis, FRANCE
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4
SoC trade-offs
ADVANTAGES:
 Cost reduction
 Shortening time to market
attack productivity bottlenecks (verification)
good design methodology
-
DISADVANTAGES:
 Increase of complexity
 Design methodology and the right verification strategy
become critical
Infineon Technologies, Sophia-Antipolis, FRANCE
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Design Methodology
 State of the art tools
 robust and proven design flow
 rigorous project management
definition phase
-
- guidelines
- checklists
- design specification
- design
phase
- VHDL coding, DFT, synthesis, floorplan, wireload model
generation, P&R
- verification
phase
- behavioural models, RTL simulation, code coverage,
GL simulation, formal verification
- documentation
phase
- functional doc.
- implementaion doc.
- verification doc.
Infineon Technologies, Sophia-Antipolis, FRANCE
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The Specification Problem
 specification detailed enough to allow RTL coding
 save time and unpleasant surprises on silicon
 serve as feasability study
 functionality, timing, performance, interfaces, physical
issues (area, power, …)
 continuously updated
 paper specification
 formal specification
 executable specification (C, C++, matlab, Cossap, …)
Infineon Technologies, Sophia-Antipolis, FRANCE
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The Specification Problem
- Overview
- Functional requirements
- Physical requirements
- Verification requirements
- Design guidelines
- Block diagram
- Interfaces
- signal names and meanings
- transaction protocols (timing diagram)
- timing specifications
- set-up and hold time on inputs
- clock to Q time for outputs
- special signals (test, analog, …)
- asynchronous signals
- clocks, resets, interrupts and their timing
- legal values for input and output datas
- checklists (paper, scripts, …)
Infineon Technologies, Sophia-Antipolis, FRANCE
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General information about ELIET
Block name
Analog Macro
PLLs
Microprocessor
DSP
Line controller
Interface
Microprocessor Memories
DSP Memories
Total (ELIET)
Cell Area (mm2)
2.00
1.10
6.09
3.07
1.60
1.60
1.76
1.75
Infineon Technologies, Sophia-Antipolis, FRANCE
Count
4
1
1
1
1
1
1
1
11
Area (mm2)
8.00
1.10
6.09
3.07
1.60
1.60
1.76
1.75
24.97
[email protected]
%
32.04
4.41
24.39
12.29
6.41
6.41
7.05
7.01
100
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Some number about ELIET
ELIET AREA DISTRIBUTION
Microprocessor
Memories
Interface
Analog Macro
Line controller
PLLs
DSP
Microprocessor
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Designed to last
 Chip design constrained by what can be verified, rather
than by the functions
 design style driven by verification (clock synchronous
synthesizable RTL)
 As the complexity of the chip increases “Pray to God
approach” is not an option
 No magic rule to getting first-time-right silicon
 maximum level of quality in each step of the development
process
 no separation between front end and back end
too many macros with the wrong aspect ratio can make the
chip unroutable or too big or can create unacceptable
delays on critical nets
accurate wire load models for DSM
 bottom up synthesis approach recommended
-
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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Designed to last
 clock distribution accurately studied
balanced clock tree with low skews
 test strategy decided at an early stage of the design
BIST for memories
full scan flops
max 1000 flops per scan chain
boundary scan
insulation and ad hoc testing for analog macros
 Guidelines and Checklists
RTL coding guidelines
coding for portability (ieee standard types, too many
subtypes, …)
guidelines for clock and reset
coding for synthesis
check code quality (profiling tools, synthesis results, ...)
no unexplained warning
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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System Integration
 Reduce the number of new gates introduced
 Massive reuse of existing proven designs
 reused parts need to be pre-verified with high degree of
quality to allow SOC verification to complete within a
reasonable time frame
 not all core configurations have been tested together
 Focus of system level simulation is on errors at macro
interconnections level
 misunderstanding of the bus protocols
different bridges to communicate between the different
busses
standardize on a single common bus architecture
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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Verification
 Main bottleneck of the development process
 Right verification strategy at each step of the design
 It is verification that drives the selection of tools and
design style
 Define the verification plan as soon as possible
a list of all test bench components
a list of required verification tools
a list of specific tests
what functionality will be verified
target code coverage
description of the regression test environment and
regression procedures
 Test bench design takes more time than the circuit design
 The entire set of test benches and test suites must be
reusable (different design teams) and portable (different
simulators)
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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Verification
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
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Test bench must be one of the deliverables
Bus functional models & bus monitors
single test bench command file
VHDL test bench guidelines
use a clock to synchronize stimuli generation
use built in textio packages
partition the test bench code in synthesizable and
behavioural
do not generate data , clocks and resets from the same
process
common strategy for the test bench for both sub-modules
and top level
the test bench has to be self-checking (no waveform
inspection required) and issue a clear error message in
case of failure (what occured, at what time, what was the
expectation, what is the result, …)
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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Verification
 Toggle coverage greater than 98%
 Timing analysis
static timing analysis and formal verification
gate level simulation in case of asynchronous parts
-
Infineon Technologies, Sophia-Antipolis, FRANCE
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Conclusion
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Mixed analog/digital 4 channel ASIC for ISDN
0.35 mm, 3.3 V technology
4 analog macros (about 2 mm2 each)
2 PLLs (about 1.10 mm2 )
microprogrammed 8 bit Harvard processor for the ISDN data
processing control (about 6.09 mm2 )
custom DSP implementing the echo cancellation algorithm
(about 3.07 mm2 )
line controller (about 1.60 mm2 )
universal external interface and iom/PCM interface
(about 1.60 mm2 )
6 ROMs for the microprogrammed processor
(about 1.76 mm2 )
1 ROM and 4 SRAMs for the DSP (about 1.75 mm2 )
Total Area of the chip ~ 51 mm2
Infineon Technologies, Sophia-Antipolis, FRANCE
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Conclusion
ELIET AREA DISTRIBUTION
M
em
o.
..
In
te
rfa
ce
op
ro
ce
ss
or
M
icr
DS
P
co
nt
ro
lle
r
Li
ne
icr
op
ro
ce
ss
or
PL
Ls
M
An
al
og
M
ac
ro
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
Infineon Technologies, Sophia-Antipolis, FRANCE
[email protected]
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Conclusion
Infineon Technologies, Sophia-Antipolis, FRANCE
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References
M.Keating, P. Bricaud
Reuse methodology manual for system-on-a-chip Designs
Kluwer Academic Publishers, 1998
A.M. Rincon, W.R. Lee, M. Slattery
The Changing Landscape of System-on-a-Chip Design
Custom Integrated Circuits Conference, 1999
R.D. Adams
System on a chip Testing
Custom Integrated Circuits Conference Educational Sessions, 1999
D.D. Warmke
Four white papers on VHDL design
Integrated System Design, 1993
Infineon Technologies, Sophia-Antipolis, FRANCE
[email protected]
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