Xilinx Constraints Guide

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Chapter 4: Xilinx Constraints You are not required to have a FROM, THRU, and TO. You can have almost any combination, such as: • FROM-TO • FROM-THRU-TO • THRU-TO • TO • FROM • FROM-THRU-THRU-THRU-TO • FROM-THRU There is no restriction on the number of THRU points. The source, THRU points, and destination can be a net, bel, comp, macro, pin, or timegroup. Constraints Guide 302 www.xilinx.com UG625 (v. 13.2) July 6, 2011
TSidentifier (Timing Specification Identifier) Architecture Support Applicable Elements Chapter 4: Xilinx Constraints TSidentifier (Timing Specification Identifier) is a basic timing constraint. TSidentifier properties beginning with the letters TS are used with the TIMESPEC in a User Constraints File (UCF). The value of TSidentifier corresponds to a specific timing specification that can then be applied to paths in the design. Applies to all FPGA devices and all CPLD devices. TIMESPEC keywords Propagation Rules It is illegal to attach TSidentifier to a net, signal, or design element. Syntax Examples The following examples show how to use this constraint with particular tools or methods. If a tool or method is not listed, you cannot use this constraint with it. UCF and NCF Syntax All the following syntax definitions use a space as a separator. The use of a colon as a separator is optional. Defining a Maximum Allowable Delay TIMESPEC “TSidentifier”=FROM “source_group” TO “dest_group” allowable_delay [units]; Defining Intermediate Points (UCF) TIMESPEC “TSidentifier”=FROM “source_group” THRU “thru_point” [THRU “thru_point1”... “thru_pointn”] TO “dest_group” allowable_delay [units]; where • identifier is an ASCII string made up of the characters A-Z, a-z, 0-9, and _ • source_group and dest_group are user-defined or predefined groups • thru_point is an intermediate point used to qualify the path, defined using a TPTHRU constraint • allowable_delay is the timing requirement value • units is an optional field to indicate the units for the allowable delay. The default units are nanoseconds (ns), but the timing number can be followed by ps, ns, micro, ms, GHz, MHz, or kHz to indicate the intended units. Defining a Linked Specification This allows you to link the timing number used in one specification to another specification. TIMESPEC “TSidentifier”=FROM “source_group” TO “dest_group” another_TSid [/ | *] number; Constraints Guide UG625 (v. 13.2) July 6, 2011 www.xilinx.com 303
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Constraints Guide UG625 (v. 13.2) J
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Table of Contents Revision History
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IBUF_DELAY_VALUE (Input Buffer Dela
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Constraint Types Attributes and Con
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Grouping Constraints for Timing Cha
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The name qualifier can include the
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Physical Constraints Mapping Note T
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Placement Constraints Chapter 1: Co
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Routing Directives Routing directiv
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Timing Constraints Chapter 1: Const
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UCF Timing Constraint Support From-
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Timing Model Constraint Priority Ch
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Chapter 2 Entry Strategies for Xili
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Constraint Schematic VHDL Verilog L
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An attribute can be declared in an
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User Constraints File (UCF) UCF Flo
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Syntax Chapter 2: Entry Strategies
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Entering Multiple Constraints File
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Chapter 2: Entry Strategies for Xil
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Running Constraints Editor As a Sta
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Defining I/O Pin Configurations Cha
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Placement LOC Constraint Assignment
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Verilog Example -------------module
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Chapter 2: Entry Strategies for Xil
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Timing Specification Priorities Cha
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Timing Constraint Strategies Chapte
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Chapter 3: Timing Constraint Strate
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The global OFFSET IN constraint for
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The PERIOD constraint syntax for th
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Example Chapter 3: Timing Constrain
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Chapter 3: Timing Constraint Strate
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The global OFFSET OUT constraints f
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Multi-Cycle Paths Chapter 3: Timing
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Xilinx Constraints Each Xilinx® co
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RANGE Chapter 4: Xilinx Constraints
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Chapter 4: Xilinx Constraints Range
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COMPRESSION GROUP PLACE Chapter 4:
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Defining From Timing Groups Chapter
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BEL (BEL) The BEL (BEL) constraint:
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BLKNM (Block Name) Architecture Sup
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BUFG (BUFG) The BUFG (BUFG) constra
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Clock Dedicated Route (CLOCK_DEDICA
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COMPGRP (Component Group) Architect
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• S_SELECTMAP16 Slave SelectMAP M
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Verilog Syntax Chapter 4: Xilinx Co
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PCF Syntax CONFIG DCI_CASCADE = ",
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Default (DEFAULT) Chapter 4: Xilinx
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Example (* KEEPER = “TRUE” *) D
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DIFF_TERM (Diff_Term) Architecture
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DIRECTED_ROUTING (Directed Routing)
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DISABLE (Disable) The DISABLE (Disa
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DRIVE (Drive) The DRIVE (Drive) con
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XCF Syntax MODEL “entity_name”
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ENABLE (Enable) The ENABLE (Enable)
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ENABLE_SUSPEND (Enable Suspend) Arc
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Constraints Editor Syntax Chapter 4
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VHDL Syntax Declare the VHDL constr
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UCF and NCF Syntax NET “signal_na
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Chapter 4: Xilinx Constraints You a
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Constraints Editor Syntax Chapter 4
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HBLKNM (Hierarchical Block Name) Ar
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HIODELAY_GROUP (HIODELAY Group) Arc
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HU_SET (HU Set) The HU_SET (HU Set)
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IBUF_DELAY_VALUE (Input Buffer Dela
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IFD_DELAY_VALUE (IFD Delay Value) T
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IN_TERM (In Term) Architecture Supp
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INREG (Input Registers) Architectur
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IOB (IOB) The IOB constraint: • I
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IOBDELAY (Input Output Block Delay)
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IODELAY_GROUP (IODELAY Group) Limit
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IOSTANDARD (Input Output Standard)
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Pinout and Area Constraints Editor
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Architecture Support Applicable Ele
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Keeper (KEEPER) Architecture Suppor
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LOC (Location) The LOC (Location) c
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Chapter 4: Xilinx Constraints The w
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LOC Range Constraint Examples Const
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PlanAhead Syntax Chapter 4: Xilinx
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Schematic LOC=P17 Chapter 4: Xilinx
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Example One Chapter 4: Xilinx Const
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Slices Prohibited Example Two Chapt
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LOCK_PINS (Lock Pins) Architecture
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where value is any chosen name unde
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MAP (Map) Architecture Support Appl
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Specify the Verilog constraint as f
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Architecture Support Applicable Ele
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MAXDELAY (Maximum Delay) Architectu
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PCF Syntax item MAXDELAY = maxvalue
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MAXSKEW (Maximum Skew) The MAXSKEW
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FPGA Editor Syntax Chapter 4: Xilin
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MIODELAY_GROUP (MIODELAY Group) Arc
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UCF and NCF Syntax Chapter 4: Xilin
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where Chapter 4: Xilinx Constraints
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Falling Edge Constraints Chapter 4:
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PlanAhead Syntax Chapter 4: Xilinx
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where Chapter 4: Xilinx Constraints
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UCF Syntax NET “clock” TNM_NET
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Attribute OUT_TERM: string; Specify
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TIMESPEC PERIOD Method Chapter 4: X
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Examples of a Primary Clock with De
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where • period is the required cl
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New PERIOD Specifications Output Pi
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Post CRC (POST_CRC) Architecture Su
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Post CRC Frequency (POST_CRC_FREQ)
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Post CRC Signal (POST_CRC_SIGNAL) A
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PRIORITY (Priority) Architecture Su
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The following are not supported: Ch
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PULLDOWN (Pulldown) Architecture Su
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PULLUP (Pullup) Architecture Suppor
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PWR_MODE (Power Mode) Architecture
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REG (Registers) The REG (Registers)
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RLOC (Relative Location) The Relati
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RLOC = X3Y4 Chapter 4: Xilinx Const
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Linking Sets Set Linkage Chapter 4:
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Chapter 4: Xilinx Constraints by th
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Linking Two HU_SET Sets Chapter 4:
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Specify the VHDL constraint as foll
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Chapter 4: Xilinx Constraints Diffe
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H_SET (H Set) Chapter 4: Xilinx Con
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Page 253 and 254: Syntax Examples Chapter 4: Xilinx C
Page 255 and 256: RLOC_RANGE (Relative Location Range
Page 257 and 258: where the relative X values (m1 and
Page 259 and 260: VHDL Syntax Declare the VHDL constr
Page 261 and 262: UCF and NCF Syntax NET “mysignal
Page 263 and 264: Verilog Syntax Chapter 4: Xilinx Co
Page 265 and 266: VHDL Syntax Chapter 4: Xilinx Const
Page 267 and 268: SLOW (Slow) The SLOW (Slow) constra
Page 269 and 270: STEPPING (Stepping) Architecture Su
Page 271 and 272: VHDL Syntax Chapter 4: Xilinx Const
Page 275 and 276: Constraints Editor Syntax Chapter 4
Page 277 and 278: Chapter 4: Xilinx Constraints The f
Page 279 and 280: TIMEGRP (Timing Group) The TIMEGRP
Page 281 and 282: Defining Latch Subgroups by Gate Se
Page 283 and 284: Chapter 4: Xilinx Constraints When
Page 285 and 286: PCF Syntax TIMEGRP name; TIMEGRP na
Page 287 and 288: Separators FROM-TO Syntax TIMESPEC
Page 289 and 290: TNM (Timing Name) Chapter 4: Xilinx
Page 291 and 292: Chapter 4: Xilinx Constraints A qua
Page 293 and 294: TNM_NET (Timing Name Net) The TNM_N
Page 295 and 296: Schematic Syntax • Attach to a ne
Page 297 and 298: TPSYNC (Timing Point Synchronizatio
Page 299 and 300: UCF and NCF Syntax NET “net_name
Page 301: Using TPTHRU in a FROM TO Constrain
Page 305 and 306: Ignoring Paths Note This form is no
Page 307 and 308: VHDL Syntax Declare the VHDL constr
Page 309 and 310: UCF and NCF Syntax Chapter 4: Xilin
Page 313 and 314: Chapter 4: Xilinx Constraints If yo
Page 315 and 316: Use Low Skew Lines (USELOWSKEWLINES
Page 317 and 318: VCCAUX (VCCAUX) Architecture Suppor
Page 319 and 320: UCF and NCF Syntax Chapter 4: Xilin
Page 321 and 322: VREF (VREF) The VREF (VREF) constra
Page 323 and 324: XBLKNM (XBLKNM) Architecture Suppor
Page 325: Additional Resources Appendix • X
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Xilinx Constraints Guide

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