Xilinx Synthesis Technology User Guide

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XST User Guide constraints specified in the XCF file will be applied ONLY to the module listed, and not to any submodules below it. To apply a constraint to the entire entity/module use the following syntax: MODEL entityname constraintname = constraintvalue; Examples: MODEL top mux_extract = false; MODEL my_design max_fanout = 256; Note If the entity my_design is instantiated several times in the design, the max_fanout=256 constraint will be applied to the each instance of my_design. To apply constraints to specific instances or signals within an entity/ module, use the INST or NET keywords: BEGIN MODEL entityname INST instancename constraintname = constraintvalue ; NET signalname constraintname = constraintvalue ; END; Examples: BEGIN MODEL crc32 INST stopwatch opt_mode = area ; INST U2 ram_style = block ; NET myclock clock_buffer = true; NET data_in iob = true; END; See the “Constraints Summary” section for the complete list of synthesis constraints that can be applied for XST. 5-12 Xilinx Development System
Design Constraints Timing Constraints vs. Non-timing Constraints From a UCF Syntax point of view all constraints supported by XST can be divided into two groups: timing constraints, and non-timing constraints For all non-timing constraints, the MODEL or BEGIN MODEL... END; constructs must be used. This is true for pure XST constraints such as FSM_EXTRACT or RAM_STYLE, as well as for implementation non-timing constraints, such as RLOC or KEEP. For timing constraints, such as PERIOD, OFFSET, TNM_NET, TIMEGRP, TIG, FROM-TO etc., XST supports native UCF syntax, including the use of wildcards and hierarchical names. Do not use these constraints inside the BEGIN MODEL... END construct, otherwise XST will issue an Error. IMPORTANT: If you specify timing constraints in the XCF file, Xilinx strongly suggests that you use '/' character as a hierarchy separator instead of '_'. Please refer to the “HIERARCHY_SEPARATOR” section of the Constraints Guide for details on its usage. Limitations When using the XCF syntax, the following limitations exist: • Nested model statements are not supported in the current release. • Instance or signal names listed between the BEGIN MODEL statement and the END statement, are only the ones visible inside the entity. Hierarchical instance or signal names are not supported. • Wildcards in instance and signal names are not supported, except in timing constraints. • Not all timing constraints are supported in the current release. Refer to the Constraint Guide for more information. • Timing constraints that were supported in the old constraint format (ALLCLOCKNETS, PERIOD, OFFSET_IN_BEFORE, OFFSET_OUT_AFTER, INPAD_TO_OUTPAD, MAX_DEALY, etc.) are not supported in XCF. See the "General Constraints" section for more information. XST User Guide 5-13
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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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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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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 247 and 248: Specifying INITs and RLOCs in HDL C
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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
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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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