Transcript Setting Design Constraints

Graduate Institute of Electronics Engineering, NTU
101-1 Under-Graduate Project
Synopsys Synthesis Overview
Speaker: 李懿玹
Adviser: Prof. An-Yeu Wu
Date: 2012/11/20
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Outline
Introduction
Synopsys Graphical Environment
Setting Design Environment
Setting Design Constraints
Synthesis Report and Analysis
Save Design and Other Issues
Example
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What is Synthesis
 Synthesis = translation + optimization
 We will get a gate level circuit with timing information after
Synthesis
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Tools We will Use
Tool
Purpose
Design Vision
User Graphical Interface of synopsys
synthesis tool
HDL Compiler
Translate Verilog descriptions into Design
Compiler
Design
Compiler
Constraint driven logic optimizer
Design Time
Static Timing Analysis (STA) engine
Design Ware
Enable synthesis using DesignWare library
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Logic Synthesis Overview
no timing info.
timing info.
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Design Vision
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HDL Compiler
 In schematic view, we can see the Verilog file is translated with
a GTECH library (the synopsys default)
GTECH
Library
no timing info
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Design Compiler
 Design Compiler maps Synopsys design block to gate level
design with a user specified library
Technology
Library
timing info
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Synopsys Related Files
Files
Purpose
.cshrc
Set path and environment variables and license check
.synopsys_dc.setup
Three distinct files are read and executed when DC is
invoked
1. system-wide (do not modify):
(e.g. $SYNOPSYS/admin/setup/)
2. User’s home directory (e.g. ~think/)
3. User’s current working directory (e.g. ~think/dv/)
 Note
 These 3 files are always read in the same order.
 Any repeated command can override the previous one.
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Synthesis Design Flow
 Develop the HDL design description
and simulate the design description to
verify that it is correct.
 Set up the .synopsys_dc.setup file.
 Set the appropriate technology,
synthetic, and symbol libraries, target
libraries, and link libraries.
 Set the necessary compilation options,
including options to read in the input
files and specify the output formats.
 Read the HDL design description.
 Define the design.
Cell
Set design attributes
Library
Define environmental conditions
Set design rules
Set realistic constraints (timing and
area goals)
 Determine a compile methodology




Specification
RTL Coding Prepare
Setting Design Environment
Setting Design Constraint
Compile Design
Analysis
Gate-level Netlist
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Synopsys On-Line Documentation (SOLD)
 Invoke Synopsys On-Line Document using the command
 unix%> acroread /usr/synopsys/sold/cur/top.pdf
 Note: whenever you find a question, check SOLD first
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Synopsys Graphical Environment
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Invoke Design Vision
 Unix%> dv &
dc_shell
command
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Read File
 Read netlists or other design
descriptions into Design
Compiler
 File/Read
 Support many different formats:
 synopsys internal formats
ddc(binary): .ddc
 Verilog: .v
 equation: .eqn
 state table: .st
 VHDL: .vhd
 PLA(Berkeley Espresso): .pla
 EDIF
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Describe the Design Environment
 You can use Design Vision to constrain your design
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Check Design
 Design/Check Design
 Execute check_design before you optimize your design
 Two types of messages are issued
 error
 Error: In design ‘bcd7segs’, cell ‘decoder’ has more pins than it’s
reference ‘d1’ has ports
 warnings
 Warning: In design ‘converter’, port ‘A’ is not connected to any nets
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Compile the Design
 The compile command optimizes and maps the current_design
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Report the Design
 From report and analysis, you can find the set attributes and the
results after optimization
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Save the Design
 Write out the design netlist after synthesis
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Different View - Design View
Hierarchy
Schematic
Symbol
View
Indicator
Current
Design
Indicator
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Setting Design Environment
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What is Design Environment
 Describes the real world environment
 Beware the defaults are not realistic conditions
 Input drive is not infinite
 Output loading is usually not zero
 Consider process, voltage, temperature (PVT) variation
 The operating environment affects the components selected
from target library and timing through your design
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Setting Design Environment





Setting Operating Environment (a)
Setting Input Driving Strength (b)
Setting Output Loading (c)
Setting Input/Output Delay (d)
Setting Wire Load Model (e)
(a) Set_operating_conditions
(d) set_input_delay
(d) set_output_delay
U1
M1
(b) set_driving_cell
U2
(c) set_load
(e) set_wire_load_model
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Setting Design Environment
 Setting Operating Environment
 Setting Input Driving Strength
 Setting Output Loading
 Setting Input/Output Delay
 Setting Wire Load Model
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Setting Operating Condition
 Attributes/Operating Environment/Operating Condition (GUI)
Maximum => slow ( setup time )
Minimum => fast (hold time)
set_operation_conditions –min_library lib_name –min condition –max_library lib_name –max condition
Ex: set_operating_conditions -min_library fast -min fast -max_library slow -max slow
Ex: set_operating_conditions -min_library fsd0a_a_generic_core_1d32vbc -min BCCOM -max_library fsd0a_a_generic_core_1d08vwc -max WCCOM
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Setting Design Environment
 Setting Operating Environment
 Setting Input Driving Strength
 Setting Output Loading
 Setting Input/Output Delay
 Setting Wire Load Model
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Setting Input Drive Impedance (GUI)
 Attribute/Operating Environment/Drive Strength
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Setting Input Drive Impedance
 Command line or script
 Take DFF as example:
set_driving_cell –library max_lib_name –lib_cell DFFX2 –pin{Q} [get_ports your_port]
or
set_drive [drive_of “max_lib_name/DFFX2/Q”] [get_ports your_port]
 For Chip design:
set_driving_cell –library IOpad_lib_name –lib_cell PDIDGZ –pin{C} [all_inputs]
or
set_drive [drive_of “IOpad_lib_name / PDIDGZ /C”] [all_inputs]
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Setting Design Environment
 Setting Operating Environment
 Setting Input Driving Strength
 Setting Output Loading
 Setting Input/Output Delay
 Setting Wire Load Model
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Setting Output Loading(GUI)
 Attribute/Operating Environment/Load
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Setting Output Loading
 Command line or script
 Take DFF as example:
Command line
load_of “max_lib_name/DFFX1/D”
script
set_load [load_of “max_lib_name/DFFX1/D”] [get_ports your_port]
 For Chip design:
Command line
load_of “IOpad_lib_name / PDT16DGZ /I”
script
set_load [load_of “IOpad_lib_name / PDT16DGZ /I”] [all_outputs]
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Setting Design Environment
 Setting Operating Environment
 Setting Input Driving Strength
 Setting Output Loading
 Setting Input/Output Delay
 Setting Wire Load Model
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Input/Output Delay
 clock cycle >= DFFclk-Qdelay + c + DFFsetup
 Input delay = DFFclk-Qdelay + a
 Output delay = e + DFFsetup
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Setting Input Delay
 Select input ports
 Attributes/Operating Environment/Input Delay
Specify
minimum
input delay
Specify
maximum
input delay
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Setting Output Delay
 Select output ports
 Attributes/Operating Environment/Output Delay
Specify
minimum
output delay
Specify
maximum
output delay
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Setting Design Environment
 Setting Operating Environment
 Setting Input Driving Strength
 Setting Output Loading
 Setting Input/Output Delay
 Setting Wire Load Model
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Setting Wire Load Model
 Wire load model estimates wire capacitance based on chip area & cell
fanout
 Setting this information during compile in order to model the design
more accurately
 Attributes/Operating Environment/Wire Load
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Setting Design Constraints
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Constraints
 Constraints are goals that the Design Compiler uses
for optimizing a design into target technology library.
 Design Rule Constraints : technology-specific
restriction; ex. maximum transition, maximum fanout,
maximum capacitance.
 Optimization Constraints : design goals and
requirements; ex. maximum delay, minimum delay,
maximum area, maximum power.
 During compile, Design Compiler attempts to meet all
constraints.
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Setting Design Constraints
 Optimization Constraints
 Basic clock constraints concept
 Constraint for Special Circuit
 Constraints for Power & Area
 Design Rule Constraints
 Final check constraints before compile
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Define Clock Specification
 What should be defined?
 Period
 Waveform
 Uncertainty
 Skew
 Latency
 Source latency (option)
 Network latency
 Transition
 Input transition
 Clock transition
 All register-to-register path are constrained now
 Combinational delay is constraint by
set_max_delay 10 -from all_input -to all_output
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Specify Clock Constrains (1/2)
 Select clock port
 Attributes/Clocks/Specify
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Specify Clock Constrains (2/2)
 creat_clock : define your clock’s waveform & respect the set-up time
requirements of all clocked flip-flops
create_clock -name "CLK" -period 10 -waveform {0 5} [get_ports CLK ]
 set_fix_hold : respect the hold time requirement of all clocked flip-flops
set_fix_hold [get_clocks CLK]
 set_dont_touch_network : do not re-buffer the clock network
set_dont_touch_network [get_clocks CLK]
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Setting Area&Power Constraint
 Attributes/OptimizationConstraints/Design Constraints
 Area Unit :
 Equivalent gate count
 um x um
 Transistors
set_max_area
0
set_max_total_power
0.0uw
set_max_dynamic_power
0.0uw
set_max_leakage_power
0.0uw
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Setting Design Constraints
Optimization Constraints
 Basic clock constraints concept
 Constraints for Special Circuit
 Constraints for Area
Design Rule Constraints
Final check constraints before compile
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Design Rule Constraints
 Vendors impose design rules that restrict how many cells are
connected to one another based on capacitance, transition ,and
fanout
 You may apply more conservative design rules to:
 Anticipate the interface environment your block will see
 Prevent the design from operating cells close to their limits, where
performance degrades rapidly
 DC respects design rules as highest priority of all in the
following order:
 set_max_transition
 set_max_fanout
 set_max_capacitance
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Setting Design Constraints
 Optimization Constraints
 Basic Clock Constraints Concept
 Constraints & STA for Special Circuit
 Constraints for Area
 Design Rule Constraints
 Final Check Constraints Before Compile
 Check Design
 Check Timing
 Check Constraints
 Save Constraints & Attributes
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Check Design
 After you set up the deign attributes & design
constraints, we recommend the next step is to check
design
 Analysis/Check Design
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Setting Design Constraints
 Optimization Constraints
 Basic Clock Constraints Concept
 Constraints & STA for Special Circuit
 Constraints for Area
 Design Rule Constraints
 Final Check Constraints Before Compile
 Check Design
 Check Timing
 Check Constraints
 Save Constraints & Attributes
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Verify Constraints are Complete in DC
 After setting constraints, verify that there are no
remaining unconstrained paths:
Check_timing
 Issues warning if unconstrained paths are found
Ex: The following end-points are not constrained for maximum delay.
End point
-------------------------------------uARM7/uA920/cp1_inst/cp1_rf_inst/reg3_reg0_
.....
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Setting Design Constraints
 Optimization Constraints
 Basic Clock Constraints Concept
 Constraints & STA for Special Circuit
 Constraints for Area
 Design Rule Constraints
 Final Check Constraints Before Compile
 Check Design
 Check Timing
 Check Constraints
 Save Constraints & Attributes
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Check Constraints
 Use the following reports to check constraints before compiling
 Design/Report XXXX
 Report Design
 In this report you can check the operating condition and wire load
model
 Report Clocks
 Notice that all the information about timing is at Timing/Report
XXX
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Setting Design Constraints
 Optimization Constraints
 Basic Clock Constraints Concept
 Constraints & STA for Special Circuit
 Constraints for Area
 Design Rule Constraints
 Final Check Constraints Before Compile
 Check Design
 Check Timing
 Check Constraints
 Save Constraints & Attributes
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Save Constraints & Attributes
 Save attributes & constraints setting as the design setup file in
dc_shell command format, use File/Save Info/Design Setup
write_script –output top_setup.tcl
 uniquify have to be added by yourself after extract the script
file
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Execute Script File
 Execute dc_shell command script file, use File/Execute Script
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Compile the Design
 The compile command optimizes and maps the current_design
 Design/Compile design
compile -boundary_optimization -map_effort medium
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Synthesis Report and Analysis
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Report
 Design / Report
 Timing / Report
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Report Design (1/2)
 Report Design Hierarchy
 Hierarchy report shows the component used in your block & hierarchy
 Design / Report Design Hierarchy
 Report Reference
 Reference report shows statistical result about reference in the design
 Design / Report Reference
 Report Net
 Net report shows the statistical results of each net
 Design / Report Nets
 Report Area
 Area report shows the um2 of the design
 Design / Report Area
 Report Power
 Design / Report Power
 Report Constraints
 Constraints report shows whether compiled design meets your constraints
 Design / Report Constraint
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Report Design (2/2)
 Extract report data by script file
 At the end of script
redirect xxx_area.rpt { report_area }
redirect xxx_power.rpt { report_power }
redirect xxx_hierarchy.rpt { report_hierarchy }
redirect xxx_nets.rpt { report_nets }
redirect xxx_constraints.rpt { report_constraints }
redirect xxx_reference.rpt { report_reference }
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Report Timing
 Timing report shows maximum or minimum delay path of design,
the default is to display one maximum delay path
redirect xxx_timing.rpt { report_timing }
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What is Slack
 Slack is the resulting margin between required & actual arrival
time
 Positive slack or zero means meet constraints
 Negative slack means violate constraints
 Setup Time Check (max delay check)
Slack_setup = Data Required Time – Data Arrival Time
 Hold Time Check (min delay check)
Slack_hold = Data Arrival Time - Data Required Time
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Report Timing Options
 Timing / Report Timing Path
Fractional part length
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Save Design and Other Issues
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Save Design
 Save your design to file before you quit Design Compiler
 File/Save saves your design in the ddc format
 File/Save As can save your design in other Write formats





Verilog: .v
VHDL: .vhd
EDIF
Synopsys formats
PLA (Berkeley Espresso): .pla
write -hierarchy -format ddc -output xxx.ddc
write -hierarchy -format verilog -output xxx.v
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Assign Problem
 Save your design in verilog format, run Verilog gate-level
simulation, and we will use Verilog In interface to translate it into
OPUS database for place & route
 If you can’t Verilog In, please check assign problem
 if there is any assignment problem, choose the block & use the
dc_shell command as follow to fix it
set verilogout_no_tri "true"
set_fix_multiple_port_nets -all -buffer_constants
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Change Naming Rule script
 Write in .synopys_dc.setup
set bus_inference_style {%s[%d]}
set bus_naming_style {%s[%d]}
set hdlout_internal_busses true
change_names –hierarchy –rule verilog
define_name_rules name_rule -allowed "A-Z a-z 0-9_“ –max_length 255 –type cell
define_name_rules name_rule -allowed "A-Z a-z 0-9_[]“ –max_length 255 –type net
define_name_rules name_rule –map {{“\\*cell\\*” “cell”}}
define_name_rules name_rule –case_insensitive
change_names –hierarchy –rules name_rule
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Gate-Level Simulation (Verilog)
 Write out gate-level netlist
 File/Save As  Verilog (for File format)
 dc_shell> write -format verilog –hierarchy -output chip.vg
 Get SDF
 File/Save Info  Design timing  Select chip.sdf
 dc_shell> write_sdf –version 2.1 -context verilog chip.sdf
 Modify your testbench file
$sdf_annotate (“the_SDF_file_name”, top_module_instance_name);
 Simulation using Verilog-XL
>> ncverilog testbench.v chip.vg –v cell_model.v +access+r
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Design Example
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Synopsys Design Vision (GUI) /
Design Compiler (text mode)
 Unix% dv&
 Unix% dc_shell
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Read Verilog File
read -format verilog {"Lab1_alu.v"}
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Schematic View

Synopsys Design analyzer will translate verilog code into G-tech
model. Double click the icon “ALU”, and click the right button
then choose Schematic view. We can get the G-tech MAP
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Symbol View

Or you can create a symbol view by click on the following symbol
view button. The symbol view is as the right window
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Set Clock (1/2)
 “Attributes”-“Specify Clock”
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Set Clock (2/2)
Specify the clock as period 10ns. (100 MHz). Don’t forget to
select “don’t touch network” and “fix hold”
create_clock -name "clk" -period 10 -waveform {"0" "5"} {"clk"}
set_dont_touch_network find( clock, "clk")
set_fix_hold clk
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Operating Condition
 set_operating_conditions "typical" -library "typical"
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Operating Environment

Select “inputA” in the Symbol View and click “Attribute”“operating environment”-“input delay”. Set 2.5ns input delay.
set_input_delay -clock clk 2.5 inputA[*]
set_input_delay -clock clk 3.8 inputB[*]
set_input_delay -clock clk 4.5 instruction[*]
set_input_delay -clock clk 5.2 reset
set_output_delay -clock clk 8 alu_out[*]
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Area & Fanout & Transition
 Click “Attribute””optimization Constraints”“Design constraints”. Set
max area is 0. Max fan-out is
8. max transition is 1.
set_max_area 0
set_max_fanout 8 find (design, ALU)
set_max_transition 1 find (design, ALU)
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Compile Design
 Click “Design”-”Compile Design”. Click “OK”, start to optimize
ALU
compile -map_effort medium
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Report
report_timing -path full -delay max -max_paths 1 -nworst 1
report_power
report_area -nosplit
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Save Files



Save gate-level netlist. Select “File”->”Save As”
Save your design. Select “File”-“Save”
Save the timing information. Select “File”-“Save Info”-”Design
Timing”, choose sdf format.
write -format verilog -hierarchy -output "ALU_s.v" find (design, ALU)
write -format db -hierarchy -output "ALU_s.db" find (design, ALU)
write_sdf ALU_s.sdf


Save script file with the constraints you have made. Use
“write_script > script_file” command or “File”-”Save Info””Design Setup“ button.
Re-run all steps automatically. Use “include script_file”
command or “File”-“Execute Script” button.
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Gate Level Simulation
 Before gate level simulation,
$sdf_annotate(“top_design.sdf”, top_design)
must be added after initial in testbench
 `timescale 1ns/10ps must be added in the 1st line of
testbench
 //RTL simulation
 Unix% ncverilog testfixture.v your_file.v +access+r
 //gate level simulation
 Unix% ncverilog testfixture_vg.v your_file.vg –v
tumc18.v +access+r
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View Waveform
 Unix% nWave&
 Open verilog.fsdb file to see the waveform
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