Xilinx Synthesis Technology User Guide

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XST User Guide Introduction Designs are usually made up of combinatorial logic and macros (for example, flip-flops, adders, subtractors, counters, FSMs, RAMs). The macros greatly improve performance of the synthesized designs. Therefore, it is important to use some coding techniques to model the macros so that they will be optimally processed by XST. During its run, XST first of all tries to recognize (infer) as many macros as possible. Then all of these macros are passed to the low level optimization step, either preserved as separate blocks or merged with surrounded logic in order to get better optimization results. This filtering depends on the type and size of a macro (for example, by default, 2-to-1 multiplexers are not preserved by the optimization engine). You have full control of the processing of inferred macros through synthesis constraints. Note Please refer to the “Design Constraints” chapter for more details on constraints and their utilization. There is detailed information about the macro processing in the XST LOG file. It contains the following: • The set of macros and associated signals, inferred by XST from the VHDL/Verilog source on a block by block basis. • The overall statistics of recognized macros. • The number and type of macros preserved by low level optimization. 2-2 Xilinx Development System
HDL Coding Techniques The following log sample displays the set of recognized macros on a block by block basis. Synthesizing Unit . Related source file is timecore.vhd. Found finite state machine for signal . ... Found 7-bit subtractor for signal . Found 7-bit subtractor for signal . Found 7-bit register for signal . Found 4-bit register for signal . ... Summary: inferred 1 Finite State Machine(s). inferred 18 D-type flip-flop(s). inferred 10 Adder/Subtracter(s). Unit synthesized. ... Synthesizing Unit . Related source file is divider.vhd. Found 18-bit up counter for signal . Found 1 1-bit 2-to-1 multiplexers. Summary: inferred 1 Counter(s). inferred 1 Multiplexer(s). Unit synthesized. ... XST User Guide 2-3
Page 1 and 2: Xilinx Synthesis Technology (XST) U
Page 3 and 4: About This Manual Manual Contents T
Page 5 and 6: Resource Description/URL About This
Page 7 and 8: Conventions Typographical This manu
Page 9 and 10: Contents About This Manual Conventi
Page 11 and 12: Contents 8-bit Shift-Left Register
Page 13 and 14: Contents Dividers .................
Page 15 and 16: Contents Verilog Flow: ............
Page 17 and 18: Contents Sequential Process with a
Page 19 and 20: Introduction Architecture Support X
Page 21 and 22: Introduction 4. Set the desired Syn
Page 23 and 24: Figure 1-1 View Synthesis Report In
Page 25: HDL Coding Techniques This chapter
Page 29 and 30: HDL Coding Techniques The following
Page 31 and 32: Table 2-1 VHDL and Verilog Examples
Page 37 and 38: Signed/Unsigned Support Registers H
Page 39 and 40: Flip-flop with Positive-Edge Clock
Page 43 and 44: VHDL Code HDL Coding Techniques Fol
Page 47 and 48: IO Pins Description CE Clock Enable
Page 49 and 50: Log File HDL Coding Techniques The
Page 51 and 52: HDL Coding Techniques Verilog Code
Page 53 and 54: HDL Coding Techniques 4-bit Latch w
Page 55 and 56: Tristates Log File HDL Coding Techn
Page 59 and 60: Counters HDL Coding Techniques XST
Page 63 and 64: HDL Coding Techniques 4-bit Unsigne
Page 65 and 66: HDL Coding Techniques entity counte
Page 67 and 68: Verilog Code HDL Coding Techniques
Page 69 and 70: HDL Coding Techniques 4-bit Unsigne
Page 73 and 74: Accumulators HDL Coding Techniques
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HDL Coding Techniques • shift mod
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Log File HDL Coding Techniques The
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Verilog Code HDL Coding Techniques
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HDL Coding Techniques 8-bit Shift-L
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VHDL Code HDL Coding Techniques Fol
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VHDL Code HDL Coding Techniques Fol
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Dynamic Shift Register module shift
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library IEEE; use IEEE.std_logic_11
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HDL Coding Techniques The following
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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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Log File HDL Coding Techniques The
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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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HDL Coding Techniques Dual-Port RAM
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HDL Coding Techniques architecture
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HDL Coding Techniques Dual-Port RAM
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VHDL Following is the VHDL code for
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Inputs Next State Function RESET CL
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FSM with 1 Process HDL Coding Techn
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Inputs FSM with 2 Processes HDL Cod
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process2 : process (state, x1) begi
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State Registers HDL Coding Techniqu
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Compact HDL Coding Techniques Compa
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Black Box Support Log File HDL Codi
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FPGA Optimization Introduction This
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Macro Generation • Number of Cloc
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Multiplexers FPGA Optimization For
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RAMs FPGA Optimization Two types of
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Flip-Flop Retiming FPGA Optimizatio
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FPGA Optimization INCREMENTAL_SYNTH
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FPGA Optimization Note In the curre
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FPGA Optimization generated NGC fil
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FPGA Optimization The problem most
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Log File Analysis FPGA Optimization
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FPGA Optimization • Tristates Thi
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FPGA Optimization NOTE: THESE TIMIN
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FPGA Optimization The start point a
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FPGA Optimization If the box_type a
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Instantiation of MUXF5 FPGA Optimiz
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Specifying INITs and RLOCs in HDL C
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FPGA Optimization for registers onl
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PCI Flow FPGA Optimization To succe
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CPLD Optimization This chapter cont
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Implementation Details for Macro Ge
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CPLD Optimization • Final results
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CPLD Optimization The CPLD fitter m
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Design Constraints Chapter 5 This c
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Synthesis Options Design Constraint
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Design Constraints Figure 5-4 Synth
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• Mux Extraction • Mux Style
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Design Constraints For FPGA device
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XST Constraint File (XCF) Design Co
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Design Constraints Timing Constrain
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Design Constraints • Add IO Buffe
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Design Constraints the components c
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HDL Constraints Design Constraints
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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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