Xilinx Constraints Guide

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Chapter 4: Xilinx Constraints SUSPEND (Suspend) Architecture Support Applicable Elements Propagation Rules The SUSPEND (Suspend) constraint: • Defines the behavior of each individual output when the FPGA device is placed in the SUSPEND power-reduction mode. • May be placed on any output or bi-directional port to specify the port to be: – tristated (3STATE) OR – pulled high (3STATE_PULLUP) or low (3STATE_PULLDOWN) OR – driven to the last value (3STATE_KEEPER or DRIVE_LAST_VALUE) • Has a default value of 3STATE Applies to Spartan®-3A and Spartan-6 devices only. Place this constraint only on a top-level output or bi-directional port targeting a Spartan-3A device or a Spartan-6 device. Place this constraint only on a top-level output or bi-directional port. 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. Values • DRIVE_LAST_VALUE • 3STATE • 3STATE_PULLUP • 3STATE_PULLDOWN • 3STATE_KEEPER Schematic Syntax Specify a new attribute to an output port or bidirectional port: • Attribute Name SUSPEND • Attribute Values See Values section above. Constraints Guide 270 www.xilinx.com UG625 (v. 13.2) July 6, 2011
VHDL Syntax Chapter 4: Xilinx Constraints Before using this constraint, declare it with the following syntax placed after the architecture declaration but before the begin statement in the top-level VHDL file: attribute SUSPEND: string; After the constraint has been declared, specify the VHDL constraint as follows: attribute SUSPEND of {top_level_port_name} : signal is "value"; Example: entity top is port (STATUS: out std_logic); end top;architecture MY_DESIGN of top is attribute SUSPEND: string; attribute SUSPEND of STATUS: signal is "DRIVE_LAST_VALUE"; begin For more information about basic VHDL syntax, see VHDL Attributes. Verilog Syntax Place the following attribute specification before the port declaration in the top-level Verilog code: (* SUSPEND="value" *) Example: module top ( (* SUSPEND="DRIVE_LAST_VALUE" *) output STATUS ); For more information about basic Verilog syntax, see Verilog Attributes. UCF and NCF Syntax Placed on an output or bi-directional port: NET "top_level_port_name" SUSPEND="value"; Example: NET "STATUS" SUSPEND="DRIVE_LAST_VALUE"; PACE Syntax To set this constraint from the Pinout and Area Constraints Editor (PACE), select the appropriate pin value from the Design Objects window. Constraints Guide UG625 (v. 13.2) July 6, 2011 www.xilinx.com 271
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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
Page 219 and 220: Post CRC Frequency (POST_CRC_FREQ)
Page 221 and 222: Post CRC Signal (POST_CRC_SIGNAL) A
Page 223 and 224: PRIORITY (Priority) Architecture Su
Page 225 and 226: The following are not supported: Ch
Page 227 and 228: PULLDOWN (Pulldown) Architecture Su
Page 229 and 230: PULLUP (Pullup) Architecture Suppor
Page 231 and 232: PWR_MODE (Power Mode) Architecture
Page 233 and 234: REG (Registers) The REG (Registers)
Page 235 and 236: RLOC (Relative Location) The Relati
Page 237 and 238: RLOC = X3Y4 Chapter 4: Xilinx Const
Page 239 and 240: Linking Sets Set Linkage Chapter 4:
Page 241 and 242: Chapter 4: Xilinx Constraints by th
Page 243 and 244: Linking Two HU_SET Sets Chapter 4:
Page 245 and 246: Specify the VHDL constraint as foll
Page 247 and 248: Chapter 4: Xilinx Constraints Diffe
Page 249 and 250: H_SET (H Set) Chapter 4: Xilinx Con
Page 251 and 252: Chapter 4: Xilinx Constraints The n
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: STEPPING (Stepping) Architecture Su
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 and 302: Using TPTHRU in a FROM TO Constrain
Page 303 and 304: TSidentifier (Timing Specification
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
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VREF (VREF) The VREF (VREF) constra
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XBLKNM (XBLKNM) Architecture Suppor
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Additional Resources Appendix • X
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