Transcript A Back-End Design Flow for Single Chip Radios

OpenAccess Gear
September 2004
David Papa1, Zhong Xiu2, Christoph Albrecht, Philip Chong, Andreas Kuehlmann3
Cadence Berkeley Labs
1University
of Michigan, 2Carnegie Mellon University, 3University of California at Berkeley
Introduction
Overview
• OpenAccess is a “community-source” industry-standard
EDA database developed to help promote tool
interoperability
• Tools using OpenAccess are becoming available in
industry, but resources for academic research are lacking
• Our project: OpenAccess Gear (OAGear)
• Current focus on four main components
– GUI: Layout and Schematic Viewer
– Static Timing Analysis
– Generic Standard Cell Placement Interface: Capo API
– Benchmarks in OpenAccess Format
– Release useful tools and libraries to enable research
– Make OpenAccess a useful platform for academia
– Provide common infrastructure for research and
benchmarking
– Adopt an open source development model
– Initiated and supported by Cadence Design Systems
Benchmarks
Technical Capabilities
Easy to read and extend, built on Qt and OpenGL
In the style and spirit of the OpenAccess standard
Layout Editor displays design directly from database
Controller operates Capo API for on-demand placement
Schematic Editor displays design’s logical connectivity
Fast OpenGL rendering scales to very large designs
“oaRegionQuery” accesses only relevant portions of the
design
OpenAccess
• Universal placer interface:
CELL(DFFX1
……
TIMING_Model(7x7
(Spline
(LOAD_AXIS …)
(INPUT_SLEW_AXIS …)
data(… …)
)
)
……
Path( CK => Q … …)
……
Setup( D => CK … …)
……
)
Cell (DFFX1) {
……
pin(Q) {
……
timing() {
related_pin : "CK";
timing_sense : non_unate;
timing_type : rising_edge;
cell_rise(7x7) {
index_1 (“… …");
index_2 (“… …");
values ( … …);
}
}
}
.lib
• Routines to:
Place
Block
Run
Timer
Weight
Nets
• “Strategy” design pattern, for placer
interoperability
• Future uses:
– Designed to be extended for Incremental flows.
– Contributions from other researchers
Bazaar
(VIEW)
CONTROLLER
“Model-View-Controller” Design
Pattern Applied to Bazaar
Static Timing Analysis: OAGear Timer
Design
oaTerm
oaGearTimerPoint
oaGearTimerExtDelay
oaInstTerm
oaGearTimerPoint
Standard Cell Library
Inst3
Inst1
Inst2
BUF1
Inst4
Inst5
The timing information is
stored using the OpenAccess
extension mechanism
(oaGearTimerPoint, …)
……
Instantiated
AND
Inst6
oaTerm
oaInst
oaGearTimerPointMaster (with arcs)
Fanin cone
#SDC constraint file
create_clock
–period 1 [get_ports {CK}]
set_input_delay 0.04
–clock CK [all_inputs]
set_output_delay 0.02
–clock CK [all_outputs]
set_driving_cell
–lib_cell INVX2 [get_ports {G*5}]
set_load 0.01 [get_ports {G2*}]
.sdc
OpenAccess
(MODEL)
Incremental timing analysis
Documentation
• When a modification occurs:
– Mark the required arrival time of
nodes in the fan-in cone invalid
– Mark the arrival time of nodes in the fan-out cone invalid
• Later if there is a query, update the timing information
Benchmarks
Modification
Query: update arrival
time, required arrival
time and slew rate
Fanout cone
Summary
• OAGear provides two sets of benchmark designs:
Capo
– place(oaLib,oaCell,oaView)
• previously too difficult!
Capo
oaNet
Generic Placement Interface + Capo API
– Pick and choose EDA algorithms
– Compose new flows and combine tools in new ways
Placement
API
• “Bazaar” = open market place
where people bring their goods
to sell
• Designed for easy to rework
code and enhanced
interoperability
– Model-View-Controller design
pattern
• Tool developers can bring their
work to our “Bazaar” to
contribute and promote them
• Built on OpenAccess for integration into other tools, e.g. placement
• Two modes: Full timing analysis and incremental timing analysis
• Different models for wires: No wire delay, bounding box model;
can be extended easily to more accurate models
• Library formats: Cadence .tlf and Synopsys .lib
• Timing constraints: Subset of .sdc constraints
• Standardized timing reports
• Detailed documentation
.tlf
– Import OpenAccess Designs and build Capo internal
data structures
– Run (potentially custom) Capo Placement Flows
– Timing driven placement flows with prototypes
Timer
Design Overview
Static Timing Analysis: OAGear Timer
GUI: Bazaar
•
•
•
•
•
•
•
GUI
GUI: Bazaar
Static Timing
Analysis
– Open Benchmarks: ISCAS89 benchmark suite and a
hypothetical 250nm standard cell library
– Restricted Benchmarks: http://crete.cadence.com/, Verilog
files and scripts are available, Faraday benchmark suite and
a 250nm GSC (Generic Standard Cell) library
• Necessary binary files to convert those designs into
OpenAccess formats
• Aimed for researchers to test their timing driven placement
algorithms and incremental placement algorithms
BENCHMARKS
OpenAccess
Timing
Library
OpenAccess
Format
Benchmarks
•
•
•
•
Planned Release Date: September 30, 2004
OAGear Home: http://oagear.sourceforge.net/
OpenAccess Home: http://openeda.si2.org/
Available as open source, free for any use
– Open development model maximizes exchange of
ideas and software between universities
– Users encouraged to contribute bug reports, patches
and functional components
• Ongoing development effort
• Possible future components: synthesis, routing, extraction