Transcript Standard Cell Libraries

Standard Cell Libraries
-- Presentation by
Abhay Dixit
Meeta Bhate
Kedar Rajpathak
What are Standard Cell Libraries
 Standard-cell libraries are fixed set of well-characterized
logic blocks.
 Basic logic functions are used several times on the same
integrated circuit.
 It will have leaf cells ranging from simple gates to latches
and flip-flops. These can then be used to build arithmetic
blocks like adders and multipliers.
 ASIC designers commonly employ the use of standard
cell libraries due to their robustness and flexibility
resulting in quick turnaround times.
Advantages of standard cell libraries
 Designers save time and money by reducing the product
development cycle time.
 Reduce risk by using predesigned, pretested and
precharacterised standard cell libraries.
 Optimisation is possible.
Disadvantages of standard cell libraries
 Time and expenses of designing or buying the standard
cell library.
 Time needed to fabricate all layers of ASIC for each new
design
 when the standard cell library must be ported to a new
fabrication process, the physical layout of all the cells
need to be changed.
 There are no naming conventions
 There are no standards for cell behavior
Classification of standard cell libraries
 Classical Libraries:
--- Theses are the most common logic elements like gates,
flip-flops, multiplexers, PAL, memories etc.
 IP (Intellectual Property) offerings:
--- These include products like gate arrays and CPLDs
which are IP offerings by many companies. Each one
providing its own features and facilities in the product.
Fragment of an ASIC Library
Class
Combinational
functions
Storage functions
Information switches
Data Operator
Element
NAND, NOT, NOR, XOR
D flip-flop,Latch, J-K
flip-flop, shift register,
RAM, ROM
Selector, Multiplexer
Adder, counter, ALU,
Decoder
MOSIS compatible design tools and cell
libraries
 MOSIS compatible cell libraries are provided by many
organisations, commercial and non-commercial both
 Commercial organisations are: Mentor Graphics,
Cadence, Artisan, Avant, Barcelona Design, Tanner
Research, LEDA systems etc.
 Non Commercial Organisations are:MSU’s SCMOS
Library, LASI, Ballistic, Magic etc.
Standard Cells Provided by Mentor
Graphics
 There are over 200 standard cells available for the 2.0 um,
1.2 um, and 0.8 um technology.
-- 2, 3, and 4-input AND, NAND, OR, NOR, AO
-- 2-input XOR and XNOR gates
-- 2-1 MUX gate
-- multiple drive strength buffers, inverters and tri-state
buffers
-- four D-type flip-flops: dff, dffs, dffr, and dffsr
-- four D-type latches: latch, latchs, latchr, latchsr
 All of these cells have quickpart models with timing for
full, backannotated simulation after layout
MGC Digital Libraries
MGC Digital Libraries (Contd..)
MGC Digital Libraries (Contd..)
MGC Digital Libraries (Contd..)
MGC Digital Libraries (Contd..)
MGC Digital Libraries (Contd..)
New Trends in Standard Cell Libraries
 In a bid to improve the performance of standard-cell
designs, vendors of place-and-route and synthesis tools
and cell libraries are teaming up to develop a technique
that is likely to lead to the death of the standard cell itself.
 Prolific Inc. (Newark, Calif.) has launched a tool called
Liquid Libraries that will create tuned cells on the fly and
insert them into the libraries used by place and route tools
 Hot on the heels of Prolific's launch, Cadabra Design
Automation (Santa Clara, Calif.) is working on a new flow
that would ultimately move library generation as far
forward as the synthesis phase, giving logic designers the
ability to tune parts of a design for low power
consumption or speed
New Trends Contd..
 Prolific is working with Cadence Design Systems, Magma
Design Automation, Monterey Design Systems and
Sapphire Design Automation..
 Cadabra is working with Avanti, Cadence, Synopsis and
Magma.
 The first fruit of the Cadabra project will be the power and
performance optimization (PPO) flow.
Important Links to Standard Cell
Libraries
a) Tanner Inc.
www.tanner.com.
b) Prolific Inc.
www. prolificinc.com
c) MOSIS organisation
www.mosis.org
MOSIS/Tech Support/MOSIS Compatible Design Tools
d) Cadabra Design
www.cadabratech.com
Automation Inc.
e) Cadence Design Systems
www.cadence.com
Inc.
Thank You