Upload
brent-watson
View
226
Download
0
Embed Size (px)
DESCRIPTION
NTU Confidential 3 Asynchronous Circuits Review (1/4) Synchronous Asynchronous
Citation preview
NTU Confidential
Introduction to the Introduction to the Applications of Applications of
Asynchronous CircuitsAsynchronous Circuits
Presenter: Po-Chun HsiehAdvisor:Tzi-Dar Chiueh
Date: 2003/09/22
2NTU Confidential
OutlineOutline• Asynchronous Circuits Review• Applications - High-Speed - Low-Power - Low Noise and Low Emission - Heterogeneous Systems• Conclusion• Reference
3NTU Confidential
Asynchronous Circuits Review Asynchronous Circuits Review (1/4)(1/4)
ComputationUnit
ComputationUnit
ACKNOWLEDGE
REQUEST
DATA
Synchronous Asynchronous
ComputationUnit
ComputationUnit
CLOCK
DATA
4NTU Confidential
Asynchronous Circuits Review Asynchronous Circuits Review (2/4)(2/4)
UnderHowto dothe
Homework
Finishthe
Homework
Writethe
ReportData Data
Bill JohnAndy
HW
12:00 am 12:00 am 12:00 am 12:00 am
Data
UnderHowto dothe
Homework
Finishthe
Homework
Writethe
Report
Data Data
Mail Mail
Bill JohnAndy
HW
12:00 am 09:00 am 06:00 am 03:00 am
Synchronous
Asynchronous
5NTU Confidential
Asynchronous Circuits Review Asynchronous Circuits Review (3/4)(3/4)
Previous ComputationB
ComputationA
Handshakecircuit
Rin Rout
Aout Ain
ComputationUnit
Reg
Rin
Aout
Rout
Ain
Rin Rout
AinAout
6NTU Confidential
Asynchronous Circuits Review Asynchronous Circuits Review (4/4)(4/4)
• Benefits:– No global clock to distribute– Early completion (Data-dependent delays and
Stage-dependent delays)– Low Power
• Drawbacks:– There are not many asynchronous tools– Not easy to test – Area cost
NTU Confidential
Applications for High-Speed Applications for High-Speed CircuitsCircuits
8NTU Confidential
Average-Case delayAverage-Case delay
[4]
9NTU Confidential
Single-Rail vs. Dual-Rail Protocol (1/2)Single-Rail vs. Dual-Rail Protocol (1/2)
• Single-Rail: Bounded delay, not easy to do early completion detection.• Sometimes we can use multi-case delay
FunctionData Data
delay
Function Data
delay
10
NTU Confidential
Single-Rail vs. Dual-Rail Protocol (2/2)Single-Rail vs. Dual-Rail Protocol (2/2)
• Dual-Rail: Encode every signal, Xi, with two wires, Xi,H and Xi,L
[1]
A,H
A,L
B,H
B,L
A,H
A,L
B,H
B,L
C,H=A,H+B,H
C,L=A,L*B,L
[2]
11
NTU Confidential
Multi-case delay look-ahead Multi-case delay look-ahead adderadder
[3]
12
NTU Confidential
Dual-rail circuitsDual-rail circuits
• Differential Cascode Voltage Switch Logic (DCVSL)• Reduced direct logic (RDL)
13
NTU Confidential
Dual-rail AdderDual-rail Adder
[4]
• A. Martin (1991)• Asynchronous adder transistor count =34
14
NTU Confidential
ComparisonComparison
Bounded delay Dual-rail
Area Better Worse
Early Completion Worse Better
Power Better ? Worse ?
NTU Confidential
Low-Power CircuitsLow-Power Circuits
•No global clock•Functions work only when needed
16
NTU Confidential
Dissipating when and where Dissipating when and where activeactive
• Functions work only when needed• In Synchronous systems, we may use Gated
ClockA input 16bits B input 16bitsOperator 2 bits
Exponent Operationcomepare
Smaller Biger
Shift Right
Multiplier & Divider
Adder & Subtractor
MUX21 Array X12
MUX21 X5
MUX21 Array
Exponent of A or B
Adder_Subtractorexponent
Exponent of Sum
Control Unit
NTU Confidential
Low Noise and Low EmissionLow Noise and Low Emission
18
NTU Confidential
What speed clock bringsWhat speed clock brings
• Noise• When voltage drops
across parasitic inductances emit EM wave
[1]
L
High frequencyCurrent
largevoltagevariation
19
NTU Confidential
• Frequency spectra of the two 80C51 microcontrollers
• In synchronous circuit with 3.6 MHz clock rate, there are a series of harmonics
[1]
NTU Confidential
Heterogeneous Systems (GALS)Heterogeneous Systems (GALS)
21
NTU Confidential
Globally-Asynchronous Globally-Asynchronous Locally-SynchronousLocally-Synchronous
• Synchronous Circuits are easy to design• Low Power: No PLL, No clock driver, Functions
work only when needed.• An approach for System-on-Chip timing
Synchronous System
Asynchronous
Synchronous System
Asynchronous
Synchronous System
Asynchronous
Mpegdecoder IP Modem Antenna
Memory
A/D
USB
CPU
22
NTU Confidential
Synchronous-Asynchronous Synchronous-Asynchronous interfaces interfaces
– asynchronous wrapper– asynchronous wrapper• h
23
NTU Confidential
ConclusionConclusion• Due to average-case delay, asynchronous
circuits have high performance.• No clock driver, No high-speed oscillator, No
PLL, and the Functions work only needed, asynchronous circuits have low power dissipation.
• No global clock No high frequency current component Low Noise and Low EM wave emission
• Due to the Increasing reuse of building blocks (IP), and integration of entire system, heterogeneous systems may be well used in the future.
24
NTU Confidential
ReferenceReference
[1] Scanning the Technology:Applications of asynchronous circuitsC. H. (Kees) van Berkel, Mark B. Josephs, and Steven M. Nowick. Proceedings of the IEEE, 87(2):223--233, February 1999.[2] Designing asynchronous circuits for low power: An IFIR filter bank for a digital hearing aidL. S. Nielsen and J. Sparsø, this issue, pp. 268-281.[3] VLSI circuits for low-power high-speed asynchronous addition S.Perri, P.Corsonello, G. Cocorullo; IEEE Trans. On VLSI Systems, In Press 2002 [4] The systematic Design of asynchronous circuits
ICCA 95[5] An asynchronous low-power 80c51 microcontrollerH. van Gageldonk, D. Baumann, K. van Berkel, D. Gloor, A. Peeters, and G. Stegmann,in Proc. Int. Symp. Advanced Researchin Asynchronous Circuits and Systems, 1998, pp. 96–107.