Xilinx Synthesis Technology User Guide

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XST User Guide RAMs Verilog Following is the Verilog code for resource sharing. module addsub(A, B, C, OPER, RES); input OPER; input [7:0] A; input [7:0] B; input [7:0] C; output [7:0] RES; reg [7:0] RES; always @(A or B or C or OPER) begin if (OPER==1'b0) RES = A + B; else RES = A - C; end endmodule If you do not want to instantiate RAM primitives in order to keep your HDL code technology independent, XST offers an automatic RAM recognition capability. XST can infer distributed as well as Block RAM. It covers the following characteristics, offered by these RAM types: • Synchronous write • Write enable • RAM enable • Asynchronous or synchronous read • Reset of the data output latches • Data output reset • Single, dual or multiple-port read • Single-port write The type of the inferred RAM depends on its description: • RAM descriptions with an asynchronous read generate a distributed RAM macro. 2-120 Xilinx Development System
HDL Coding Techniques • RAM descriptions with a synchronous read generate a Block RAM macro. In some cases, a Block RAM macro can actually be implemented with Distributed RAM. The decision on the actual RAM implementation is done by the macro generator. Here is the list of VHDL/Verilog templates that will be described below: • Single-Port RAM with asynchronous read • Single-Port RAM with "false" synchronous read • Single-Port RAM with synchronous read (Read Through) • Single-Port RAM with Enable • Dual-Port RAM with asynchronous read • Dual-Port RAM with false synchronous read • Dual-Port RAM with synchronous read (Read Through) • Dual-Port RAM with One Enable Controlling Both Ports • Dual-Port RAM with Enable Controlling Each Port • Dual-Port RAM with Different Clocks • Multiple-Port RAM descriptions If a given template can be implemented using Block and Distributed RAM, XST will implement BLOCK ones. You can use the ram_style attribute to control RAM implementation and select a desirable RAM type. Please refer to the “Design Constraints” chapter for more details. Please note that the following features specifically available with Block RAM are not yet supported: • Dual write port • Parity bits • Different aspect ratios on each port Please refer to the “FPGA Optimization” chapter for more details on RAM implementation. XST User Guide 2-121
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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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Log File HDL Coding Techniques The
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HDL Coding Techniques 8-bit Shift-L
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Page 93 and 94: Dynamic Shift Register module shift
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Page 115 and 116: Priority Encoders Log File HDL Codi
Page 117 and 118: Verilog Logical Shifters HDL Coding
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Page 125 and 126: Unsigned 8-bit Adder HDL Coding Tec
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Page 133 and 134: Unsigned 8-bit Adder/Subtractor HDL
Page 135 and 136: Comparators (=, /=,=) HDL Coding Te
Page 137 and 138: HDL Coding Techniques this, XST can
Page 139 and 140: Dividers HDL Coding Techniques VHDL
Page 143: B C A OPER +/- RES OPER X8984 HDL C
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Page 149 and 150: HDL Coding Techniques VHDL The foll
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Page 153 and 154: HDL Coding Techniques VHDL The foll
Page 155 and 156: Log File HDL Coding Techniques The
Page 157 and 158: VHDL Following is the VHDL code for
Page 159 and 160: HDL Coding Techniques Single-Port R
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Page 181 and 182: HDL Coding Techniques architecture
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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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Verilog HDL Coding Techniques Follo
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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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Verilog Following is the Verilog co
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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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Verilog Following is the Verilog co
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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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