Xilinx Synthesis Technology User Guide

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XST User Guide and new NGC file will be generated as shown in the following log file segment. ... ================================================================ * * Low Level Synthesis * ================================================================ Incremental synthesis: Unit is up to date ... Incremental synthesis: Unit is up to date ... Incremental synthesis: Unit is up to date ... Incremental synthesis: Unit is up to date ... ... Optimizing unit ... Optimizing unit ... Optimizing unit ... Optimizing unit ... Optimizing unit ... ================================================================ ... If you have: • previously run XST in non-incremental mode and then switched to incremental mode or • the decomposition of the design was changed you must delete all previously generated NGC files before continuing. Otherwise XST will issue an error. If in the previous example, you were to add "incremental_synthesis=true" to the block LEVA_1, XST will give you the following error: ERROR:Xst:624 - Could not find instance of cell in 3-16 Xilinx Development System
FPGA Optimization The problem most likely occurred because the design was previously run in non-incremental synthesis mode. To fix the problem, remove the existing NGC files from the project directory. Speed Optimization Under Area Constraint. Starting from 5.1i release XST performs timing optimization under area constraint. This option "Slice Utilization Ratio" is available under the XST Synthesis Options in the Process Properties dialog box in Project Navigator. By default this constraint is set to 100% of selected device size. This constraint has influence at low level synthesis only (it does not control inference process). If this constraint is specified, XST will make area estimation, and if the specified constraint is met, XST will continue timing optimization trying not to exceed the constraint. If t the size of the design is more than requested, then XST will try to reduce the area first and if the area constraint is met, then will start timing optimization. In the following example the area constrain was specified as 100% and initial estimation shows that in fact it occupies 102% of the selected device. XST starts optimization and reaches 95%. ... ================================================================ * * Low Level Synthesis * ================================================================ Found area constraint ratio of 100 (+ 5) on block tge, actual ratio is 102. Optimizing block to meet ratio 100 (+ 5) of 1536 slices : Area constraint is met for block , final ratio is 95. ================================================================ ... If the area constraint cannot be met, then XST will ignore it during timing optimization and will run low level synthesis in order to reach the best frequency. In the following example, the target area XST User Guide 3-17
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Xilinx Synthesis Technology (XST) U
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About This Manual Manual Contents T
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Resource Description/URL About This
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Conventions Typographical This manu
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Contents About This Manual Conventi
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Contents 8-bit Shift-Left Register
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Contents Dividers .................
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Contents Verilog Flow: ............
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Contents Sequential Process with a
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Introduction Architecture Support X
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Introduction 4. Set the desired Syn
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Figure 1-1 View Synthesis Report In
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HDL Coding Techniques This chapter
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HDL Coding Techniques The following
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Table 2-1 VHDL and Verilog Examples
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Signed/Unsigned Support Registers H
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Flip-flop with Positive-Edge Clock
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VHDL Code HDL Coding Techniques Fol
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IO Pins Description CE Clock Enable
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Log File HDL Coding Techniques The
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HDL Coding Techniques Verilog Code
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HDL Coding Techniques 4-bit Latch w
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Tristates Log File HDL Coding Techn
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Counters HDL Coding Techniques XST
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HDL Coding Techniques 4-bit Unsigne
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HDL Coding Techniques entity counte
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Verilog Code HDL Coding Techniques
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HDL Coding Techniques 4-bit Unsigne
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Accumulators HDL Coding Techniques
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HDL Coding Techniques • shift mod
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HDL Coding Techniques 8-bit Shift-L
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Dynamic Shift Register module shift
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library IEEE; use IEEE.std_logic_11
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neither Full nor Parallel module no
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Related Constraints Related constra
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HDL Coding Techniques entity mux is
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Decoders Log File HDL Coding Techni
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VHDL (One-Cold) Following is the VH
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VHDL Following is the VHDL code. li
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Priority Encoders Log File HDL Codi
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Verilog Logical Shifters HDL Coding
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Example 1 HDL Coding Techniques The
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Verilog Arithmetic Operations Follo
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Unsigned 8-bit Adder HDL Coding Tec
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HDL Coding Techniques Verilog Follo
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Simple Signed 8-bit Adder HDL Codin
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Unsigned 8-bit Adder/Subtractor HDL
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Comparators (=, /=,=) HDL Coding Te
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HDL Coding Techniques this, XST can
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Dividers HDL Coding Techniques VHDL
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B C A OPER +/- RES OPER X8984 HDL C
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HDL Coding Techniques • RAM descr
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HDL Coding Techniques entity raminf
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HDL Coding Techniques VHDL The foll
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HDL Coding Techniques Verilog The f
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HDL Coding Techniques VHDL The foll
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VHDL Following is the VHDL code for
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HDL Coding Techniques Single-Port R
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Verilog HDL Coding Techniques Follo
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HDL Coding Techniques Single-Port R
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Verilog Following is the Verilog co
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VHDL HDL Coding Techniques Followin
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Dual-Port RAM with Asynchronous Rea
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Verilog Following is the Verilog co
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VHDL HDL Coding Techniques Followin
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HDL Coding Techniques Dual-Port RAM
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Page 197 and 198: Inputs Next State Function RESET CL
Page 199 and 200: FSM with 1 Process HDL Coding Techn
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Page 207 and 208: State Registers HDL Coding Techniqu
Page 209 and 210: Compact HDL Coding Techniques Compa
Page 211 and 212: Black Box Support Log File HDL Codi
Page 215 and 216: FPGA Optimization Introduction This
Page 217 and 218: Macro Generation • Number of Cloc
Page 219 and 220: Multiplexers FPGA Optimization For
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Page 223 and 224: Flip-Flop Retiming FPGA Optimizatio
Page 225 and 226: FPGA Optimization INCREMENTAL_SYNTH
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Page 233 and 234: Log File Analysis FPGA Optimization
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Page 237 and 238: FPGA Optimization NOTE: THESE TIMIN
Page 239 and 240: FPGA Optimization The start point a
Page 241 and 242: FPGA Optimization If the box_type a
Page 243 and 244: Instantiation of MUXF5 FPGA Optimiz
Page 247 and 248: Specifying INITs and RLOCs in HDL C
Page 249 and 250: FPGA Optimization for registers onl
Page 251 and 252: PCI Flow FPGA Optimization To succe
Page 253 and 254: CPLD Optimization This chapter cont
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Page 257 and 258: CPLD Optimization • Final results
Page 259 and 260: CPLD Optimization The CPLD fitter m
Page 261 and 262: Design Constraints Chapter 5 This c
Page 263 and 264: Synthesis Options Design Constraint
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FPGA Constraints (non-timing) Desig
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Design Constraints • Number of Cl
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Design Constraints This constraint
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Timing Constraints Design Constrain
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Design Constraints See the “CLOCK
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Design Constraints The following ti
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Design Constraints • TIMEGRP TIME
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Design Constraints See the “INPAD
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Constraint Name clock_buffer bufgdl
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Constraint Name move_last- _stage m
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Constraint Name xor_collapse yes, n
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Constraint Name synthesis/ synopsis
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Design Constraints The following ta
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*Also Supported in XCF format. Impl
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Design Constraints The binary equiv
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Table 5-5 Third Party Constraints N
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Table 5-5 Third Party Constraints N
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Constraints Precedence Design Const
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VHDL Language Support Chapter 6 Thi
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VHDL Language Support 'W' means wea
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VHDL Language Support compiled in t
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Record Types Objects in VHDL MATRIX
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Entity Declaration VHDL Language Su
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VHDL Language Support Example 6-2 g
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VHDL Language Support Example 6-3 4
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egin Y 13), port map (X,Y,C1); C2
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VHDL Language Support Example 6-5 M
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VHDL Language Support Example 6-8 N
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Example 6-10 Combinatorial Process
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VHDL Language Support Example 6-12
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For...Loop Statement VHDL Language
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Sequential Process without a Sensit
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egin if RST = '1' then DO
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Multiple Wait Statements Descriptio
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Functions and Procedures VHDL Langu
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VHDL Language Support Example 6-24
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STANDARD Package VHDL Language Supp
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VHDL Language Support Note Function
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Packages Enumeration Types Integer
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Table 6-4 Objects VHDL Language Sup
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Wait Statement Loop Statement Table
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VHDL Reserved Words The following t
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Verilog Language Support Chapter 7
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Behavioral Verilog Features Verilog
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Verilog Language Support Example 7-
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Table 7-1 Expressions Bitwise Negat
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Modules Verilog Language Support In
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Procedural Assignments Verilog Lang
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Verilog Language Support Casez trea
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While Loops Verilog Language Suppor
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Verilog Language Support Example 7-
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Verilog Language Support The main l
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Verilog Language Support • You ca
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Example 7-9 Function Declaration an
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Blocking Versus Non-Blocking Proced
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Include Files Verilog Language Supp
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Verilog Language Support Each insta
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Parameters Verilog Language Support
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Verilog Language Support • Design
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Verilog Meta Comments Verilog Langu
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Table 7-4 Data Types Registers Vect
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Table 7-8 Design Hierarchy Module d
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Verilog Reserved Keywords Verilog L
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Command Line Mode Introduction Chap
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Command Line Mode • Script File
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Command Line Mode • Second column
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Table 8-4 HDL Options (VHDL and Ver
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Command Line Mode Table 8-6 Target
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Command Line Mode • To get a list
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Elaborate Command Time Command Comm
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♦ smallcntr.vhd Command Line Mode
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Command Line Mode You can improve t
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Command Line Mode Sometimes, XST is
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XST Shell Command Line Mode To use
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Case 2 Command Line Mode Each desig
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Log File Analysis Introduction This
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Quiet Mode Timing Report Log File A
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RAM Style : Auto ROM Extraction : y
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Synthesizing Unit . Related source
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# Counters : 2 # 4-bit up counter :
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Log File Analysis Data Path: sixty_
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CPLD Log File Log File Analysis The
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Analyzing Entity (Architecture ).
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Log File Analysis =================
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XST Naming Conventions This appendi
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