Xilinx Synthesis Technology User Guide

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XST User Guide Note the following limitations. • Flip-flop retiming will not be applied to flip-flops that have the IOB=TRUE property. • Flip-flops will not be moved forward if the flip-flop or the output signal has the KEEP property. • Flip-flops will not be moved backward if the input signal has the KEEP property. • Instantiated flip-flops will not be moved. • Flip-flops with both a set and a reset will not be moved. Flip-flop retiming can be controlled by applying the register_balancing, move_first_stage, and move_last_stage constraints. Incremental Synthesis Flow. The main goal of Incremental Synthesis flow is to reduce the overall time the designer spends in completing a project. This can be achieved by allowing you to re-synthesizing only the modified portions of the design instead of the entire design. We may consider two main categories of incremental synthesis: • Block Level: The synthesis tool re-synthesizes the entire block if at least one modification was made inside this block. • Gate or LUT Level: The synthesis tool tries to identify the exact changes made in the design and generates the final netlist with minimal changes XST supports block level incremental synthesis with some limitations. Incremental Synthesis is implemented using two constraints: INCREMENTAL_SYNTHESIS, and RESYNTHESIZE. INCREMENTAL_SYNTHESIS: Use the INCREMENTAL_SYNTHESIS constraint to control the decomposition of the design on several groups. • If this constraint is applied to a specific block, this block with all its descendents will be considered as one group, until the next 3-10 Xilinx Development System
FPGA Optimization INCREMENTAL_SYNTHESIS attribute is found. During synthesis, XST will generate a single NGC file for the group. • In the current release, you cannot apply the INCREMENTAL_SYNTHESIS constraint to a block that is instantiated multiple times. If this occurs, XST will issue the following error: ERROR:Xst:1344 - Cannot support incremental synthesis on block my_sub instanciated several times. • If a a single block is changed then the entire group will be resynthesized and new NGC file(s) will be generated. • Please note that starting from 5.2i release the INCREMENTAL_SYNTHESIS switch is NO LONGER accessible via the “Xilinx Specific Options” tab from Synthesis Properties. This directive is only available via VHDL attributes or Verilog meta-comments, or via an XST constraint file. Example Figure xxx shows how blocks are grouped by use of the INCREMENTAL_SYNTHESIS constraint. Consider the following: • LEVA, LEVA_1, LEVA_2, my_add, my_sub as one group • LEVB, my_and, my_or and my_sub as another group. • TOP is considered separately as a single group. XST User Guide 3-11
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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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Page 177 and 178: HDL Coding Techniques Dual-Port RAM
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Page 181 and 182: HDL Coding Techniques architecture
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Page 195 and 196: VHDL Following is the VHDL code for
Page 197 and 198: Inputs Next State Function RESET CL
Page 199 and 200: FSM with 1 Process HDL Coding Techn
Page 201 and 202: Inputs FSM with 2 Processes HDL Cod
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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
Page 221 and 222: RAMs FPGA Optimization Two types of
Page 223: Flip-Flop Retiming FPGA Optimizatio
Page 227 and 228: FPGA Optimization Note In the curre
Page 229 and 230: FPGA Optimization generated NGC fil
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Page 233 and 234: Log File Analysis FPGA Optimization
Page 235 and 236: FPGA Optimization • Tristates Thi
Page 237 and 238: FPGA Optimization NOTE: THESE TIMIN
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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
Page 255 and 256: Implementation Details for Macro Ge
Page 257 and 258: CPLD Optimization • Final results
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Page 261 and 262: Design Constraints Chapter 5 This c
Page 263 and 264: Synthesis Options Design Constraint
Page 265 and 266: Design Constraints Figure 5-4 Synth
Page 267 and 268: • Mux Extraction • Mux Style
Page 269 and 270: Design Constraints For FPGA device
Page 271 and 272: XST Constraint File (XCF) Design Co
Page 273 and 274: 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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