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DS031 October 14, 2003 www.xilinx.comProduct Specification 1-800-255-7778
© 2003 Xilinx, Inc. All rights reserved. All Xilinx trademarks, registered trademarks, patents, and disclaimers are as listed at http://www.xilinx.com/legal.htm. All other trademarks and registered trademarks are the property of their respective owners. All specifications are subject to change without notice.
This document includes all four modules of the Virtex-II Platform FPGA data sheet.
Module 1: Introduction and OverviewDS031-1 (v2.0) August 1, 20037 pages
• Summary of Features• General Description• Device/Package Combinations and Maximum I/O• Ordering Information
Module 2: Functional DescriptionDS031-2 (v3.1) October 14, 200340 pages
• Detailed Description• Digitally Controlled Impedance (DCI)• Configurable Logic Blocks (CLBs)• Sum of Products• 3-State Buffers• 18-Kb Block SelectRAM™ Resources• 18-Bit x 18-Bit Multipliers• Global Clock Multiplexer Buffers• Digital Clock Manager (DCM)• Active Interconnect Technology• Creating a Design• Configuration
Module 3: DC and Switching CharacteristicsDS031-3 (v3.1) October 14, 200338 pages
• Electrical Characteristics• Performance Characteristics• Switching Characteristics• Pin-to-Pin Output Parameter Guidelines• Pin-to-Pin Input Parameter Guidelines• DCM Timing Parameters
Module 4: Pinout InformationDS031-4 (v2.0) August 1, 2003225 pages
• Pin Definitions• Pinout Tables
- CS144 Chip-Scale BGA Package- FG256 Fine-Pitch BGA Package- FG456 Fine-Pitch BGA Package- FG676 Fine-Pitch BGA Package- BG575 Standard BGA Package- BG728 Standard BGA Package- FF896 Flip-Chip Fine-Pitch BGA Package- FF1152 Flip-Chip Fine-Pitch BGA Package- FF1517 Flip-Chip Fine-Pitch BGA Package- BF957Flip-Chip BGA Package
IMPORTANT NOTE: The Virtex-II Platform FPGA data sheet is created and published in separate modules. This completeversion is provided for easy downloading and searching of the complete document. Page, figure, and table numbers beginat 1 for each module, and each module has its own Revision History at the end. Use the PDF "Bookmarks" pane for easynavigation in this volume.
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Virtex™-II Platform FPGAs: Complete Data Sheet
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DS031-1 (v2.0) August 1, 2003 www.xilinx.com Module 1 of 4Product Specification 1-800-255-7778 1
Summary of Virtex-II Features• Industry First Platform FPGA Solution
• IP-Immersion Architecture- Densities from 40K to 8M system gates- 420 MHz internal clock speed (Advance Data)- 840+ Mb/s I/O (Advance Data)
• SelectRAM™ Memory Hierarchy- 3 Mb of dual-port RAM in 18 Kbit block SelectRAM
resources- Up to 1.5 Mb of distributed SelectRAM resources
• High-Performance Interfaces to External Memory- DRAM interfaces
· SDR / DDR SDRAM· Network FCRAM · Reduced Latency DRAM
- SRAM interfaces· SDR / DDR SRAM· QDR™ SRAM
- CAM interfaces
• Arithmetic Functions- Dedicated 18-bit x 18-bit multiplier blocks- Fast look-ahead carry logic chains
• Flexible Logic Resources- Up to 93,184 internal registers / latches with Clock
Enable- Up to 93,184 look-up tables (LUTs) or cascadable
16-bit shift registers- Wide multiplexers and wide-input function support- Horizontal cascade chain and sum-of-products
support- Internal 3-state bussing
• High-Performance Clock Management Circuitry- Up to 12 DCM (Digital Clock Manager) modules
· Precise clock de-skew· Flexible frequency synthesis· High-resolution phase shifting
- 16 global clock multiplexer buffers
• Active Interconnect Technology- Fourth generation segmented routing structure- Predictable, fast routing delay, independent of fanout
• SelectIO™-Ultra Technology- Up to 1,108 user I/Os- 19 single-ended and six differential standards
- Programmable sink current (2 mA to 24 mA) per I/O- Digitally Controlled Impedance (DCI) I/O: on-chip
termination resistors for single-ended I/O standards- PCI-X compatible (133 MHz and 66 MHz) at 3.3V- PCI compliant (66 MHz and 33 MHz) at 3.3V- CardBus compliant (33 MHz) at 3.3V- Differential Signaling
· 840 Mb/s Low-Voltage Differential Signaling I/O (LVDS) with current mode drivers
· Bus LVDS I/O· Lightning Data Transport (LDT) I/O with current
driver buffers· Low-Voltage Positive Emitter-Coupled Logic
(LVPECL) I/O· Built-in DDR input and output registers
- Proprietary high-performance SelectLink Technology· High-bandwidth data path· Double Data Rate (DDR) link· Web-based HDL generation methodology
• Supported by Xilinx Foundation™ and Alliance Series™ Development Systems- Integrated VHDL and Verilog design flows- Compilation of 10M system gates designs- Internet Team Design (ITD) tool
• SRAM-Based In-System Configuration- Fast SelectMAP configuration- Triple Data Encryption Standard (DES) security
option (Bitstream Encryption)- IEEE 1532 support - Partial reconfiguration- Unlimited reprogrammability- Readback capability
• 0.15 µm 8-Layer Metal Process with 0.12 µm High-Speed Transistors
• 1.5V (VCCINT) Core Power Supply, Dedicated 3.3V VCCAUX Auxiliary and VCCO I/O Power Supplies
• IEEE 1149.1 Compatible Boundary-Scan Logic Support
• Flip-Chip and Wire-Bond Ball Grid Array (BGA) Packages in Three Standard Fine Pitches (0.80 mm, 1.00 mm, and 1.27 mm)
• 100% Factory Tested
0 7Virtex™-II Platform FPGAs:Introduction and Overview
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General DescriptionThe Virtex-II family is a platform FPGA developed for highperformance from low-density to high-density designs thatare based on IP cores and customized modules. The familydelivers complete solutions for telecommunication, wire-less, networking, video, and DSP applications, includingPCI, LVDS, and DDR interfaces.
The leading-edge 0.15 µm / 0.12 µm CMOS 8-layer metalprocess and the Virtex-II architecture are optimized for highspeed with low power consumption. Combining a wide vari-ety of flexible features and a large range of densities up to10 million system gates, the Virtex-II family enhances pro-grammable logic design capabilities and is a powerful alter-native to mask-programmed gates arrays. As shown inTable 1, the Virtex-II family comprises 11 members, rangingfrom 40K to 8M system gates.
PackagingOfferings include ball grid array (BGA) packages with0.80 mm, 1.00 mm, and 1.27 mm pitches. In addition to tra-ditional wire-bond interconnects, flip-chip interconnect isused in some of the BGA offerings. The use of flip-chipinterconnect offers more I/Os than is possible in wire-bondversions of the similar packages. Flip-chip constructionoffers the combination of high pin count with high thermalcapacity.
Table 2 shows the maximum number of user I/Os available.The Virtex-II device/package combination table (Table 6 atthe end of this section) details the maximum number of I/Osfor each device and package using wire-bond or flip-chiptechnology.
Table 1: Virtex-II Field-Programmable Gate Array Family Members
DeviceSystem Gates
CLB (1 CLB = 4 slices = Max 128 bits)
Multiplier Blocks
SelectRAM Blocks
DCMsMax I/O Pads(1)
Array Row x Col. Slices
Maximum Distributed RAM Kbits
18 Kbit Blocks
Max RAM (Kbits)
XC2V40 40K 8 x 8 256 8 4 4 72 4 88
XC2V80 80K 16 x 8 512 16 8 8 144 4 120
XC2V250 250K 24 x 16 1,536 48 24 24 432 8 200
XC2V500 500K 32 x 24 3,072 96 32 32 576 8 264
XC2V1000 1M 40 x 32 5,120 160 40 40 720 8 432
XC2V1500 1.5M 48 x 40 7,680 240 48 48 864 8 528
XC2V2000 2M 56 x 48 10,752 336 56 56 1,008 8 624
XC2V3000 3M 64 x 56 14,336 448 96 96 1,728 12 720
XC2V4000 4M 80 x 72 23,040 720 120 120 2,160 12 912
XC2V6000 6M 96 x 88 33,792 1,056 144 144 2,592 12 1,104
XC2V8000 8M 112 x 104 46,592 1,456 168 168 3,024 12 1,108
Notes: 1. See details in Table 2, “Maximum Number of User I/O Pads”.
Table 2: Maximum Number of User I/O Pads
Device Wire-Bond Flip-Chip
XC2V40 88 -
XC2V80 120 -
XC2V250 200 -
XC2V500 264 -
XC2V1000 328 432
XC2V1500 392 528
XC2V2000 - 624
XC2V3000 516 720
XC2V4000 - 912
XC2V6000 - 1,104
XC2V8000 - 1,108
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Architecture
Virtex-II Array OverviewVirtex-II devices are user-programmable gate arrays with various configurable elements. The Virtex-II architecture is optimized for high-density and high-performance logic designs. As shown in Figure 1, the programmable device is comprised of input/output blocks (IOBs) and internal configurable logic blocks (CLBs).
Programmable I/O blocks provide the interface between package pins and the internal configurable logic. Most popular and leading-edge I/O standards are supported by the programmable IOBs.
The internal configurable logic includes four major elementsorganized in a regular array.
• Configurable Logic Blocks (CLBs) provide functional elements for combinatorial and synchronous logic, including basic storage elements. BUFTs (3-state buffers) associated with each CLB element drive dedicated segmentable horizontal routing resources.
• Block SelectRAM memory modules provide large 18 Kbit storage elements of dual-port RAM.
• Multiplier blocks are 18-bit x 18-bit dedicated multipliers.
• DCM (Digital Clock Manager) blocks provide self-calibrating, fully digital solutions for clock distribution delay compensation, clock multiplication and division, coarse- and fine-grained clock phase shifting.
A new generation of programmable routing resources calledActive Interconnect Technology interconnects all of theseelements. The general routing matrix (GRM) is an array ofrouting switches. Each programmable element is tied to aswitch matrix, allowing multiple connections to the generalrouting matrix. The overall programmable interconnection ishierarchical and designed to support high-speed designs.
All programmable elements, including the routingresources, are controlled by values stored in static memory
cells. These values are loaded in the memory cells duringconfiguration and can be reloaded to change the functionsof the programmable elements.
Virtex-II FeaturesThis section briefly describes Virtex-II features.
Input/Output Blocks (IOBs)IOBs are programmable and can be categorized as follows:
• Input block with an optional single-data-rate or double-data-rate (DDR) register
• Output block with an optional single-data-rate or DDR register, and an optional 3-state buffer, to be driven directly or through a single or DDR register
• Bidirectional block (any combination of input and output configurations)
These registers are either edge-triggered D-type flip-flopsor level-sensitive latches.
IOBs support the following single-ended I/O standards:
• LVTTL, LVCMOS (3.3V, 2.5V, 1.8V, and 1.5V)
• PCI-X compatible (133 MHz and 66 MHz) at 3.3V
• PCI compliant (66 MHz and 33 MHz) at 3.3V
• CardBus compliant (33 MHz) at 3.3V
Figure 1: Virtex-II Architecture Overview
Global Clock Mux
DCM DCM IOB
CLBProgrammable I/Os
Block SelectRAM Multiplier
Configurable Logic
DS031_28_100900
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• GTL and GTLP
• HSTL (Class I, II, III, and IV)
• SSTL (3.3V and 2.5V, Class I and II)
• AGP-2X
The digitally controlled impedance (DCI) I/O feature auto-matically provides on-chip termination for each I/O element.
The IOB elements also support the following differential sig-naling I/O standards:
• LVDS
• BLVDS (Bus LVDS)
• ULVDS
• LDT
• LVPECL
Two adjacent pads are used for each differential pair. Two orfour IOB blocks connect to one switch matrix to access therouting resources.
Configurable Logic Blocks (CLBs)CLB resources include four slices and two 3-state buffers.Each slice is equivalent and contains:
• Two function generators (F & G)
• Two storage elements
• Arithmetic logic gates
• Large multiplexers
• Wide function capability
• Fast carry look-ahead chain
• Horizontal cascade chain (OR gate)
The function generators F & G are configurable as 4-inputlook-up tables (LUTs), as 16-bit shift registers, or as 16-bitdistributed SelectRAM memory.
In addition, the two storage elements are either edge-trig-gered D-type flip-flops or level-sensitive latches.
Each CLB has internal fast interconnect and connects to aswitch matrix to access general routing resources.
Block SelectRAM Memory
The block SelectRAM memory resources are 18 Kb ofdual-port RAM, programmable from 16K x 1 bit to 512 x 36bits, in various depth and width configurations. Each port istotally synchronous and independent, offering three"read-during-write" modes. Block SelectRAM memory iscascadable to implement large embedded storage blocks.Supported memory configurations for dual-port and sin-gle-port modes are shown in Table 3.
A multiplier block is associated with each SelectRAM mem-ory block. The multiplier block is a dedicated 18 x 18-bitmultiplier and is optimized for operations based on the blockSelectRAM content on one port. The 18 x 18 multiplier canbe used independently of the block SelectRAM resource.Read/multiply/accumulate operations and DSP filter struc-tures are extremely efficient.
Both the SelectRAM memory and the multiplier resourceare connected to four switch matrices to access the generalrouting resources.
Global ClockingThe DCM and global clock multiplexer buffers provide acomplete solution for designing high-speed clockingschemes.
Up to 12 DCM blocks are available. To generate de-skewedinternal or external clocks, each DCM can be used to elimi-nate clock distribution delay. The DCM also provides 90-,180-, and 270-degree phase-shifted versions of its outputclocks. Fine-grained phase shifting offers high-resolutionphase adjustments in increments of 1/256 of the clockperiod. Very flexible frequency synthesis provides a clockoutput frequency equal to any M/D ratio of the input clockfrequency, where M and D are two integers. For the exacttiming parameters, see Virtex-II Electrical Characteris-tics.
Virtex-II devices have 16 global clock MUX buffers, with upto eight clock nets per quadrant. Each global clock MUXbuffer can select one of the two clock inputs and switchglitch-free from one clock to the other. Each DCM block isable to drive up to four of the 16 global clock MUX buffers.
Routing ResourcesThe IOB, CLB, block SelectRAM, multiplier, and DCM ele-ments all use the same interconnect scheme and the sameaccess to the global routing matrix. Timing models areshared, greatly improving the predictability of the perfor-mance of high-speed designs.
There are a total of 16 global clock lines, with eight availableper quadrant. In addition, 24 vertical and horizontal longlines per row or column as well as massive secondary andlocal routing resources provide fast interconnect. Virtex-IIbuffered interconnects are relatively unaffected by netfanout and the interconnect layout is designed to minimizecrosstalk.
Horizontal and vertical routing resources for each row orcolumn include:
• 24 long lines• 120 hex lines• 40 double lines• 16 direct connect lines (total in all four directions)
Table 3: Dual-Port And Single-Port Configurations
16K x 1 bit 2K x 9 bits
8K x 2 bits 1K x 18 bits
4K x 4 bits 512 x 36 bits
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Boundary Scan
Boundary scan instructions and associated data registerssupport a standard methodology for accessing and config-uring Virtex-II devices that complies with IEEE standards1149.1 — 1993 and 1532. A system mode and a test modeare implemented. In system mode, a Virtex-II device per-forms its intended mission even while executing non-testboundary-scan instructions. In test mode, boundary-scantest instructions control the I/O pins for testing purposes.The Virtex-II Test Access Port (TAP) supports BYPASS,PRELOAD, SAMPLE, IDCODE, and USERCODE non-testinstructions. The EXTEST, INTEST, and HIGHZ test instruc-tions are also supported.
ConfigurationVirtex-II devices are configured by loading data into internalconfiguration memory, using the following five modes:
• Slave-serial mode• Master-serial mode
• Slave SelectMAP mode
• Master SelectMAP mode• Boundary-Scan mode (IEEE 1532)
A Data Encryption Standard (DES) decryptor is availableon-chip to secure the bitstreams. One or two triple-DES keysets can be used to optionally encrypt the configurationinformation.
Readback and Integrated Logic Analyzer
Configuration data stored in Virtex-II configuration memorycan be read back for verification. Along with the configura-tion data, the contents of all flip-flops/latches, distributedSelectRAM, and block SelectRAM memory resources canbe read back. This capability is useful for real-time debug-ging.
The Integrated Logic Analyzer (ILA) core and software pro-vides a complete solution for accessing and verifyingVirtex-II devices.
Virtex-II Device/Package Combinations and Maximum I/OWire-bond and flip-chip packages are available. Table 4 andTable 5 show the maximum possible number of user I/Os inwire-bond and flip-chip packages, respectively. Table 6shows the number of available user I/Os for all device/pack-age combinations.
• CS denotes wire-bond chip-scale ball grid array (BGA) (0.80 mm pitch).
• FG denotes wire-bond fine-pitch BGA (1.00 mm pitch). • FF denotes flip-chip fine-pitch BGA (1.00 mm pitch).• BG denotes standard BGA (1.27 mm pitch).• BF denotes flip-chip BGA (1.27 mm pitch).
The number of I/Os per package include all user I/Os exceptthe 15 control pins (CCLK, DONE, M0, M1, M2, PROG_B,PWRDWN_B, TCK, TDI, TDO, TMS, HSWAP_EN, DXN,DXP, and RSVD) and VBATT.
Table 4: Wire-Bond Packages Information
Package CS144 FG256 FG456 FG676 BG575 BG728
Pitch (mm) 0.80 1.00 1.00 1.00 1.27 1.27
Size (mm) 12 x 12 17 x 17 23 x 23 27 x 27 31 x 31 35 x 35
I/Os 92 172 324 484 408 516
Table 5: Flip-Chip Packages Information
Package FF896 FF1152 FF1517 BF957
Pitch (mm) 1.00 1.00 1.00 1.27
Size (mm) 31 x 31 35 x 35 40 x 40 40 x 40
I/Os 624 824 1,108 684
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Virtex-II Ordering Information
Table 6: Virtex-II Device/Package Combinations and Maximum Number of Available I/Os (Advance Information)
Package
Available I/Os
XC2V40
XC2V80
XC2V250
XC2V500
XC2V1000
XC2V1500
XC2V2000
XC2V3000
XC2V4000
XC2V6000
XC2V8000
CS144 88 92 92 - - - - - - - -
FG256 88 120 172 172 172 - - - - - -
FG456 - - 200 264 324 - - - - - -
FG676 - - - - - 392 456 484 - - -
FF896 - - - - 432 528 624 - - - -
FF1152 - - - - - - - 720 824 824 824
FF1517 - - - - - - - - 912 1,104 1,108
BG575 - - - - 328 392 408 - - - -
BG728 - - - - - - - 516 - - -
BF957 - - - - - - 624 684 684 684 -
Notes: 1. All devices in a particular package are pinout (footprint) compatible. In addition, the FG456 and FG676 packages are compatible, as
are the FF896 and FF1152 packages.
Figure 2: Virtex-II Ordering Information
Example: XC2V1000-5FG456C
Device Type Temperature RangeC = Commercial (Tj = 0˚C to +85˚C)I = Industrial (Tj = –40˚C to +100˚C)
Number of Pins
Package Type
Speed Grade(-4, -5, -6)
DS031_35_033001
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Revision HistoryThis section records the change history for this module of the data sheet.
Virtex-II Data SheetThe Virtex-II Data Sheet contains the following modules:
• Virtex™-II Platform FPGAs: Introduction and Overview (Module 1)
• Virtex™-II Platform FPGAs: Detailed Description (Module 2)
• Virtex™-II Platform FPGAs: DC and Switching Characteristics (Module 3)
• Virtex™-II Platform FPGAs: Pinout Information (Module 4)
Date Version Revision
11/07/00 1.0 Early access draft.
12/06/00 1.1 Initial release.
01/15/01 1.2 Added values to the tables in the Virtex-II Performance Characteristics and Virtex-II Switching Characteristics sections.
01/25/01 1.3 The data sheet was divided into four modules (per the current style standard).
04/02/01 1.5 Skipped v1.4 to sync up modules. Reverted to traditional double-column format.
07/30/01 1.6 Made minor changes to items listed under Summary of Virtex-II Features.
10/02/01 1.7 Minor edits.
07/16/02 1.8 Updated Virtex-II Device/Package Combinations shown in Table 6.
09/26/02 1.9 Updated Table 2 and Table 6 to reflect supported Virtex-II Device/Package Combinations.
08/01/03 2.0 All Virtex-II devices and speed grades now Production. See Table 13, Module 3.
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Detailed Description
Input/Output Blocks (IOBs)Virtex-II I/O blocks (IOBs) are provided in groups of two orfour on the perimeter of each device. Each IOB can be usedas input and/or output for single-ended I/Os. Two IOBs canbe used as a differential pair. A differential pair is alwaysconnected to the same switch matrix, as shown in Figure 1.
IOB blocks are designed for high performances I/Os, sup-porting 19 single-ended standards, as well as differentialsignaling with LVDS, LDT, Bus LVDS, and LVPECL.
Note: Differential I/Os must use the same clock.
Supported I/O StandardsVirtex-II IOB blocks feature SelectI/O-Ultra inputs and out-puts that support a wide variety of I/O signaling standards.In addition to the internal supply voltage (VCCINT = 1.5V),output driver supply voltage (VCCO) is dependent on the I/Ostandard (see Table 1). An auxiliary supply voltage(VCCAUX = 3.3 V) is required, regardless of the I/O stan-dard used. For exact supply voltage absolute maximum rat-ings, see DC Input and Output Levels in Module 3.
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Figure 1: Virtex-II Input/Output Tile
IOBPAD4
IOBPAD3
Differential Pair
IOBPAD2
IOBPAD1
Differential Pair
SwitchMatrix
DS031_30_101600
Table 1: Supported Single-Ended I/O Standards
I/OStandard
OutputVCCO
InputVCCO
InputVREF
Board Termination Voltage (VTT)
LVTTL 3.3 3.3 N/R(3) N/R
LVCMOS33 3.3 3.3 N/R N/R
LVCMOS25 2.5 2.5 N/R N/R
LVCMOS18 1.8 1.8 N/R N/R
LVCMOS15 1.5 1.5 N/R N/R
PCI33_3 3.3 3.3 N/R N/R
PCI66_3 3.3 3.3 N/R N/R
PCI-X 3.3 3.3 N/R N/R
GTL Note (1) Note (1) 0.8 1.2
GTLP Note (1) Note (1) 1.0 1.5
HSTL_I 1.5 N/R 0.75 0.75
HSTL_II 1.5 N/R 0.75 0.75
HSTL_III 1.5 N/R 0.9 1.5
HSTL_IV 1.5 N/R 0.9 1.5
HSTL_I_18 1.8 N/R 0.9 0.9
HSTL_II_18 1.8 N/R 0.9 0.9
HSTL_III _18 1.8 N/R 1.1 1.8
HSTL_IV_18 1.8 N/R 1.1 1.8
SSTL18_I(2) 1.8 N/R 0.9 0.9
SSTL18_II 1.8 N/R 0.9 0.9
SSTL2_I 2.5 N/R 1.25 1.25
SSTL2_II 2.5 N/R 1.25 1.25
SSTL3_I 3.3 N/R 1.5 1.5
SSTL3_II 3.3 N/R 1.5 1.5
AGP-2X/AGP 3.3 N/R 1.32 N/R
Notes: 1. VCCO of GTL or GTLP should not be lower than the
termination voltage or the voltage seen at the I/O pad.2. SSTL18_I is not a JEDEC-supported standard.3. N/R = no requirement.
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All of the user IOBs have fixed-clamp diodes to VCCO andto ground. As outputs, these IOBs are not compatible orcompliant with 5V I/O standards. As inputs, these IOBs arenot normally 5V tolerant, but can be used with 5V I/O stan-dards when external current-limiting resistors are used. Formore details, see the “5V Tolerant I/Os“ Tech Topic atwww.xilinx.com.
Table 3 lists supported I/O standards with Digitally Con-trolled Impedance. See Digitally Controlled Impedance(DCI), page 8.
Table 2: Supported Differential Signal I/O Standards
I/O StandardOutputVCCO
Input VCCO
InputVREF
OutputVOD
LVPECL_33 3.3 N/R(1) N/R 490 mV to 1.22V
LDT_25 2.5 N/R N/R 0.430 - 0.670
LVDS_33 3.3 N/R N/R 0.250 - 0.400
LVDS_25 2.5 N/R N/R 0.250 - 0.400
LVDSEXT_33 3.3 N/R N/R 0.330 - 0.700
LVDSEXT_25 2.5 N/R N/R 0.330 - 0.700
BLVDS_25 2.5 N/R N/R 0.250 - 0.450
ULVDS_25 2.5 N/R N/R 0.430 - 0.670
Notes: 1. N/R = no requirement.
Table 3: Supported DCI I/O Standards
I/OStandard
OutputVCCO
InputVCCO
InputVREF
TerminationType
LVDCI_33(1) 3.3 3.3 N/R(4) Series
LVDCI_DV2_33(1) 3.3 3.3 N/R Series
LVDCI_25(1) 2.5 2.5 N/R Series
LVDCI_DV2_25(1) 2.5 2.5 N/R Series
LVDCI_18(1) 1.8 1.8 N/R Series
LVDCI_DV2_18(1) 1.8 1.8 N/R Series
LVDCI_15(1) 1.5 1.5 N/R Series
LVDCI_DV2_15(1) 1.5 1.5 N/R Series
GTL_DCI 1.2 1.2 0.8 Single
GTLP_DCI 1.5 1.5 1.0 Single
HSTL_I_DCI 1.5 1.5 0.75 Split
HSTL_II_DCI 1.5 1.5 0.75 Split
HSTL_III_DCI 1.5 1.5 0.9 Single
HSTL_IV_DCI 1.5 1.5 0.9 Single
HSTL_I_DCI_18 1.8 1.8 0.9 Split
HSTL_II_DCI_18 1.8 1.8 0.9 Split
HSTL_III_DCI_18 1.8 1.8 1.1 Single
HSTL_IV_DCI_18 1.8 1.8 1.1 Single
SSTL18_I_DCI(3) 1.8 1.8 0.9 Split
SSTL18_II_DCI 1.8 1.8 0.9 Split
SSTL2_I_DCI(2) 2.5 2.5 1.25 Split
SSTL2_II_DCI(2) 2.5 2.5 1.25 Split
SSTL3_I_DCI(2) 3.3 3.3 1.5 Split
SSTL3_II_DCI(2) 3.3 3.3 1.5 Split
LVDS_33_DCI 3.3 3.3 N/R Split
LVDS_25_DCI 2.5 2.5 N/R Split
LVDSEXT_33_DCI 3.3 3.3 N/R Split
LVDSEXT_25_DCI 2.5 2.5 N/R Split
Notes: 1. LVDCI_XX and LVDCI_DV2_XX are LVCMOS controlled
impedance buffers, matching the reference resistors or half of the reference resistors.
2. These are SSTL compatible.3. SSTL18_I is not a JEDEC-supported standard.4. N/R = no requirement.
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Logic Resources
IOB blocks include six storage elements, as shown inFigure 2.
Each storage element can be configured either as anedge-triggered D-type flip-flop or as a level-sensitive latch.On the input, output, and 3-state path, one or two DDR reg-isters can be used.
Double data rate is directly accomplished by the two regis-ters on each path, clocked by the rising edges (or fallingedges) from two different clock nets. The two clock signalsare generated by the DCM and must be 180 degrees out ofphase, as shown in Figure 3. There are two input, output,and 3-state data signals, each being alternately clocked out.
For each storage element, the SRHIGH, SRLOW, INIT0,and INIT1 attributes are independent. Synchronous orasynchronous set / reset is consistent in an IOB block.
All the control signals have independent polarity. Anyinverter placed on a control input is automatically absorbed.
Each register or latch (independent of all other registers orlatches) (see Figure 4) can be configured as follows:
• No set or reset
• Synchronous set• Synchronous reset• Synchronous set and reset• Asynchronous set (preset)• Asynchronous reset (clear)• Asynchronous set and reset (preset and clear)
The synchronous reset overrides a set, and an asynchro-nous clear overrides a preset.
Figure 2: Virtex-II IOB Block
Reg
OCK1
Reg
OCK2
Reg
ICK1
Reg
ICK2
DDR muxInput
PAD
3-State
Reg
OCK1
Reg
OCK2
DDR mux
Output
IOB
DS031_29_100900
Figure 3: Double Data Rate Registers
D1
CLK1
DDR MUX
Q1
FDDR
D2
CLK2
(50/50 duty cycle clock)
CLOCK
Q Q
Q2
D1
CLK1
DDR MUX
DCM
Q1
FDDR
D2
CLK2
Q2
180° 0°
DS031_26_100900
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Input/Output Individual OptionsEach device pad has optional pull-up and pull-down in allSelectI/O-Ultra configurations. Each device pad hasoptional weak-keeper in LVTTL, LVCMOS, and PCISelectI/O-Ultra configurations, as illustrated in Figure 5.
Values of the optional pull-up and pull-down resistors are inthe range 10 - 60 KΩ, which is the specification for VCCOwhen operating at 3.3V (from 3.0 to 3.6V only). The clampdiode is always present, even when power is not.
The optional weak-keeper circuit is connected to each userI/O pad. When selected, the circuit monitors the voltage on
the pad and weakly drives the pin High or Low. If the pin isconnected to a multiple-source signal, the weak-keeper
Figure 4: Register / Latch Configuration in an IOB Block
FFLATCH
SR REV
D1 Q1
CE
CK1
FFLATCH
SR REV
D2
FF1
FF2DDR MUX
Q2
CECK2
REV
SR
(O/T) CLK1
(OQ or TQ)
(O/T) CE
(O/T) 1
(O/T) CLK2
(O/T) 2
Attribute INIT1INIT0SRHIGHSRLOW
Attribute INIT1INIT0SRHIGHSRLOW
Reset TypeSYNCASYNC
DS031_25_110300
Sharedby all
registers
Figure 5: LVTTL, LVCMOS or PCI SelectI/O-Ultra Standards
VCCO
VCCO
VCCO
WeakKeeper
ProgramDelay
OBUF
IBUF
Program Current
ClampDiode
10-60KΩ
10-60KΩ
PAD
VCCAUX = 3.3V
DS031_23_011601
VCCINT = 1.5V
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holds the signal in its last state if all drivers are disabled.Maintaining a valid logic level in this way eliminates buschatter. An enabled pull-up or pull-down overrides theweak-keeper circuit.
LVTTL sinks and sources current up to 24 mA. The currentis programmable for LVTTL and LVCMOS SelectI/O-Ultrastandards (see Table 4). Drive-strength and slew-rate con-trols for each output driver, minimize bus transients. ForLVDCI and LVDCI_DV2 standards, drive strength andslew-rate controls are not available.
Figure 6 shows the SSTL2, SSTL3, and HSTL configura-tions. HSTL can sink current up to 48 mA. (HSTL IV)
All pads are protected against damage from electrostaticdischarge (ESD) and from over-voltage transients. Virtex-IIuses two memory cells to control the configuration of an I/Oas an input. This is to reduce the probability of an I/O con-figured as an input from flipping to an output when sub-jected to a single event upset (SEU) in space applications.
Prior to configuration, all outputs not involved in configura-tion are forced into their high-impedance state. Thepull-down resistors and the weak-keeper circuits are inac-tive. The dedicated pin HSWAP_EN controls the pull-upresistors prior to configuration. By default, HSWAP_EN isset high, which disables the pull-up resistors on user I/Opins. When HSWAP_EN is set low, the pull-up resistors areactivated on user I/O pins.
All Virtex-II IOBs support IEEE 1149.1 compatible boundaryscan testing.
Input Path
The Virtex-II IOB input path routes input signals directly tointernal logic and / or through an optional input flip-flop orlatch, or through the DDR input registers. An optional delayelement at the D-input of the storage element eliminatespad-to-pad hold time. The delay is matched to the internalclock-distribution delay of the Virtex-II device, and whenused, assures that the pad-to-pad hold time is zero.
Each input buffer can be configured to conform to any of thelow-voltage signaling standards supported. In some ofthese standards the input buffer utilizes a user-suppliedthreshold voltage, VREF. The need to supply VREF imposesconstraints on which standards can be used in the samebank. See I/O banking description.
Output PathThe output path includes a 3-state output buffer that drivesthe output signal onto the pad. The output and / or the3-state signal can be routed to the buffer directly from theinternal logic or through an output / 3-state flip-flop or latch,or through the DDR output / 3-state registers.
Each output driver can be individually programmed for awide range of low-voltage signaling standards. In most sig-naling standards, the output High voltage depends on anexternally supplied VCCO voltage. The need to supply VCCOimposes constraints on which standards can be used in thesame bank. See I/O banking description.
I/O BankingSome of the I/O standards described above require VCCOand VREF voltages. These voltages are externally suppliedand connected to device pins that serve groups of IOBblocks, called banks. Consequently, restrictions exist aboutwhich I/O standards can be combined within a given bank.
Eight I/O banks result from dividing each edge of the FPGAinto two banks, as shown in Figure 7 and Figure 8. Eachbank has multiple VCCO pins, all of which must be con-
Table 4: LVTTL and LVCMOS Programmable Currents (Sink and Source)
SelectI/O-Ultra Programmable Current (Worst-Case Guaranteed Minimum)
LVTTL 2 mA 4 mA 6 mA 8 mA 12 mA 16 mA 24 mA
LVCMOS33 2 mA 4 mA 6 mA 8 mA 12 mA 16 mA 24 mA
LVCMOS25 2 mA 4 mA 6 mA 8 mA 12 mA 16 mA 24 mA
LVCMOS18 2 mA 4 mA 6 mA 8 mA 12 mA 16 mA n/a
LVCMOS15 2 mA 4 mA 6 mA 8 mA 12 mA 16 mA n/a
Figure 6: SSTL or HSTL SelectI/O-Ultra Standards
VCCO
OBUF
VREF
ClampDiode
PAD
VCCAUX = 3.3VVCCINT = 1.5V
DS031_24_100900
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nected to the same voltage. This voltage is determined bythe output standards in use.
Some input standards require a user-supplied thresholdvoltage (VREF), and certain user-I/O pins are automaticallyconfigured as VREF inputs. Approximately one in six of theI/O pins in the bank assume this role.
VREF pins within a bank are interconnected internally, andconsequently only one VREF voltage can be used withineach bank. However, for correct operation, all VREF pins inthe bank must be connected to the external reference volt-age source.
The VCCO and the VREF pins for each bank appear in thedevice pinout tables. Within a given package, the number ofVREF and VCCO pins can vary depending on the size ofdevice. In larger devices, more I/O pins convert to VREFpins. Since these are always a superset of the VREF pinsused for smaller devices, it is possible to design a PCB thatpermits migration to a larger device if necessary.
All VREF pins for the largest device anticipated must be con-nected to the VREF voltage and not used for I/O. In smallerdevices, some VCCO pins used in larger devices do not con-nect within the package. These unconnected pins can beleft unconnected externally, or, if necessary, they can beconnected to VCCO to permit migration to a larger device.
Rules for Combining I/O Standards in the Same Bank
The following rules must be obeyed to combine differentinput, output, and bi-directional standards in the same bank:
1. Combining output standards only. Output standards with the same output VCCO requirement can be combined in the same bank. Compatible example:
SSTL2_I and LVDS_25_DCI outputsIncompatible example:
SSTL2_I (output VCCO = 2.5V) and LVCMOS33 (output VCCO = 3.3V) outputs
2. Combining input standards only. Input standards with the same input VCCO and input VREF requirements can be combined in the same bank.Compatible example:
LVCMOS15 and HSTL_IV inputs
Incompatible example:LVCMOS15 (input VCCO = 1.5V) and LVCMOS18 (input VCCO = 1.8V) inputs
Incompatible example:HSTL_I_DCI_18 (VREF = 0.9V) and HSTL_IV_DCI_18 (VREF = 1.1V) inputs
3. Combining input standards and output standards. Input standards and output standards with the same input VCCO and output VCCO requirement can be combined in the same bank. Compatible example:
LVDS_25 output and HSTL_I input
Incompatible example:LVDS_25 output (output VCCO = 2.5V) and HSTL_I_DCI_18 input (input VCCO = 1.8V)
4. Combining bi-directional standards with input or output standards. When combining bi-directional I/O with other standards, make sure the bi-directional standard can meet rules 1 through 3 above.
5. Additional rules for combining DCI I/O standards.
a. No more than one Single Termination type (input oroutput) is allowed in the same bank.Incompatible example:
HSTL_IV_DCI input and HSTL_III_DCI input
b. No more than one Split Termination type (input or output) is allowed in the same bank.Incompatible example:
HSTL_I_DCI input and HSTL_II_DCI input
The implementation tools will enforce these design rules.
Figure 7: Virtex-II I/O Banks: Top View for Wire-Bond Packages (CS, FG, & BG)
Figure 8: Virtex-II I/O Banks: Top View for Flip-Chip Packages (FF & BF)
ug002_c2_014_112900
Bank 0 Bank 1
Bank 5 Bank 4
Ban
k 7
Ban
k 6
Ban
k 2
Ban
k 3
ds031_66_112900
Bank 1 Bank 0
Bank 4 Bank 5
Ban
k 2
Ban
k 3
Ban
k 7
Ban
k 6
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Table 5 summarizes all standards and voltage supplies.
Table 5: Summary of Voltage Supply Requirements for All Input and Output Standards
I/O Standard
VCCO VREF Termination Type
Output Input Input Output Input
LVDS_33
3.3
N/R
N/R(1) N/R N/R
LVDSEXT_33 N/R N/R N/R
LVPECL_33 N/R N/R N/R
SSTL3_I 1.5 N/R N/R
SSTL3_II 1.5 N/R N/R
AGP 1.32 N/R N/R
LVTTL
3.3
N/R N/R N/R
LVCMOS33 N/R N/R N/R
LVDCI_33 N/R Series N/R
LVDCI_DV2_33 N/R Series N/R
PCI33_3 N/R N/R N/R
PCI66_3 N/R N/R N/R
PCIX N/R N/R N/R
LVDS_33_DCI N/R N/R Split
LVDSEXT_33_DCI N/R N/R Split
SSTL3_I_DCI 1.5 N/R Split
SSTL3_II_DCI 1.5 Split Split
LVDS_25
2.5
N/R
N/R N/R N/R
LVDSEXT_25 N/R N/R N/R
LDT_25 N/R N/R N/R
ULVDS_25 N/R N/R N/R
BLVDS_25 N/R N/R N/R
SSTL2_I 1.25 N/R N/R
SSTL2_II 1.25 N/R N/R
LVCMOS25
2.5
N/R N/R N/R
LVDCI_25 N/R Series N/R
LVDCI_DV2_25 N/R Series N/R
LVDS_25_DCI N/R N/R Split
LVDSEXT_25_DCI N/R N/R Split
SSTL2_I_DCI 1.25 N/R Split
SSTL2_II_DCI 1.25 Split Split
HSTL_III_18
1.8
N/R
1.1 N/R N/R
HSTL_IV_18 1.1 N/R N/R
HSTL_I_18 0.9 N/R N/R
HSTL_II_18 0.9 N/R N/R
SSTL18_I 0.9 N/R N/R
SSTL18_II 0.9 N/R N/R
LVCMOS18
1.8
N/R N/R N/R
LVDCI_18 N/R Series N/R
LVDCI_DV2_18 N/R Series N/R
HSTL_III_DCI_18 1.1 N/R Single
HSTL_IV_DCI_18 1.1 Single Single
HSTL_I_DCI_18 0.9 N/R Split
HSTL_II_DCI_18 0.9 Split Split
SSTL18_I_DCI 0.9 N/R Split
SSTL18_II_DCI 0.9 Split Split
HSTL_III
1.5
N/R
0.9 N/R N/R
HSTL_IV 0.9 N/R N/R
HSTL_I 0.75 N/R N/R
HSTL_II 0.75 N/R N/R
LVCMOS15
1.5
N/R N/R N/R
LVDCI_15 N/R Series N/R
LVDCI_DV2_15 N/R Series N/R
GTLP_DCI 1 Single Single
HSTL_III_DCI 0.9 N/R Single
HSTL_IV_DCI 0.9 Single Single
HSTL_I_DCI 0.75 N/R Split
HSTL_II_DCI 0.75 Split Split
GTL_DCI 1.2 1.2 0.8 Single Single
GTLPN/R N/R
1 N/R N/R
GTL 0.8 N/R N/R
Notes: 1. N/R = no requirement.
Table 5: Summary of Voltage Supply Requirements for All Input and Output Standards (Continued)
I/O Standard
VCCO VREF Termination Type
Output Input Input Output Input
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Digitally Controlled Impedance (DCI)Today’s chip output signals with fast edge rates require ter-mination to prevent reflections and maintain signal integrity.High pin count packages (especially ball grid arrays) cannot accommodate external termination resistors.
Virtex-II XCITE DCI provides controlled impedance driversand on-chip termination for single-ended and differentialI/Os. This eliminates the need for external resistors, andimproves signal integrity. The DCI feature can be used onany IOB by selecting one of the DCI I/O standards.
When applied to inputs, DCI provides input parallel termina-tion. When applied to outputs, DCI provides controlledimpedance drivers (series termination) or output paralleltermination.
DCI operates independently on each I/O bank. When a DCII/O standard is used in a particular I/O bank, external refer-ence resistors must be connected to two dual-function pinson the bank. These resistors, voltage reference of N transis-tor (VRN) and the voltage reference of P transistor (VRP)are shown in Figure 9.
When used with a terminated I/O standard, the value ofresistors are specified by the standard (typically 50 Ω).When used with a controlled impedance driver, the resistorsset the output impedance of the driver within the specifiedrange (25 Ω to 100 Ω). For all series and parallel termina-tions listed in Table 6 and Table 7, the reference resistorsmust have the same value for any given bank. One percentresistors are recommended.
The DCI system adjusts the I/O impedance to match the twoexternal reference resistors, or half of the reference resis-tors, and compensates for impedance changes due to volt-age and/or temperature fluctuations. The adjustment isdone by turning parallel transistors in the IOB on or off.
Controlled Impedance Drivers (Series Termination)DCI can be used to provide a buffer with a controlled outputimpedance. It is desirable for this output impedance tomatch the transmission line impedance (Z). Virtex-II inputbuffers also support LVDCI and LVDCI_DV2 I/O standards.
Controlled Impedance Drivers (Parallel Termination)DCI also provides on-chip termination for SSTL3, SSTL2,HSTL (Class I, II, III, or IV), and GTL/GTLP receivers ortransmitters on bidirectional lines.Table 7 lists the on-chip parallel terminations available in Vir-tex-II devices. VCCO must be set according to Table 3. Notethat there is a VCCO requirement for GTL_DCI andGTLP_DCI, due to the on-chip termination resistor.
Figure 9: DCI in a Virtex-II BankDS031_50_101200
VCCO
GND
DCI
DCI
DCI
DCI
VRN
VRP
1 Bank
RREF (1%)
RREF (1%)
Figure 10: Internal Series Termination
Table 6: SelectI/O-Ultra Controlled Impedance Buffers
VCCO DCI DCI Half Impedance
3.3 V LVDCI_33 LVDCI_DV2_33
2.5 V LVDCI_25 LVDCI_DV2_25
1.8 V LVDCI_18 LVDCI_DV2_18
1.5 V LVDCI_15 LVDCI_DV2_15
Table 7: SelectI/O-Ultra Buffers With On-Chip Parallel Termination
I/O StandardExternal
TerminationOn-Chip
Termination
SSTL3 Class I SSTL3_I SSTL3_I_DCI(1)
SSTL3 Class II SSTL3_II SSTL3_II_DCI(1)
SSTL2 Class I SSTL2_I SSTL2_I_DCI(1)
SSTL2 Class II SSTL2_II SSTL2_II_DCI(1)
HSTL Class I HSTL_I HSTL_I_DCI
HSTL Class II HSTL_II HSTL_II_DCI
HSTL Class III HSTL_III HSTL_III_DCI
HSTL Class IV HSTL_IV HSTL_IV_DCI
GTL GTL GTL_DCI
GTLP GTLP GTLP_DCI
Notes: 1. SSTL Compatible
Z
IOB
Z
Virtex-II DCI
DS031_51_110600VCCO = 3.3 V, 2.5 V, 1.8 V or 1.5 V
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Figure 11 provides examples illustrating the use of the HSTL_I_DCI, HSTL_II_DCI, HSTL_III_DCI, and HSTL_IV_DCI I/Ostandards. For a complete list, see the Virtex-II User Guide.
Figure 11: HSTL DCI Usage Examples
Virtex-II DCI
R R
VCCO VCCO
R R
VCCO VCCO
R
VCCO
R
VCCO
Virtex-II DCI
Virtex-II DCI
R
VCCO
R
VCCO
Virtex-II DCI
R R
VCCO/2 VCCO/2
2R
Virtex-II DCI
2R
R
VCCO VCCO/2
Virtex-II DCI
2R
R
VCCO/2
2R
VCCO
2R
Virtex-II DCI
2R
VCCO
Virtex-II DCI
2R
2R
VCCO
DS031_65a_100201
Conventional
DCI TransmitConventionalReceive
ConventionalTransmitDCI Receive
DCI TransmitDCI Receive
Bidirectional
ReferenceResistor
RecommendedZ0
(1)
VRN = VRP = R = Z0
50 Ω
VRN = VRP = R = Z0
50 Ω
VRN = VRP = R = Z0
50 Ω
VRN = VRP = R = Z0
50 Ω
HSTL_I HSTL_II HSTL_III HSTL_IV
N/A N/A
Virtex-II DCI
R
VCCO
R
VCCO
R
VCCO
Virtex-II DCI
R
VCCO
Virtex-II DCI
Z0
R
VCCO/2
Virtex-II DCI
R
VCCO/2
Virtex-II DCI
2R
2R
VCCO
Virtex-II DCIVirtex-II DCI
2R
2R
VCCO
Z0
Z0
Z0
Z0Z0
Z0Z0
Z0
Z0Z0Z0
Z0
Z0
Z0
Z0
Virtex-II DCI
Virtex-II DCI
Z0
Virtex-II DCI
2R
2R
VCCO
2R
2R
VCCO
Virtex-II DCI
Z0
Virtex-II DCI
R
VCCO
R
VCCO
Note:1. Z0 is the recommended PCB trace impedance.
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Figure 12 provides examples illustrating the use of the SSTL2_I_DCI, SSTL2_II_DCI, SSTL3_I_DCI, and SSTL3_II_DCI I/Ostandards. For a complete list, see the Virtex-II User Guide.
Figure 12: SSTL DCI Usage Examples
DS031_65b_112502
Conventional
DCI TransmitConventionalReceive
ConventionalTransmitDCI Receive
DCI TransmitDCI Receive
Bidirectional
ReferenceResistor
Recommended Z0
(2)
VRN = VRP = R = Z0
50 Ω
VRN = VRP = R = Z0
50 Ω
VRN = VRP = R = Z0
50 Ω
VRN = VRP = R = Z0
50 Ω
SSTL2_I SSTL2_II SSTL3_I SSTL3_II
N/A N/A
Virtex-II DCI
Z0
R
VCCO/2
Z0R/2
R R
VCCO/2 VCCO/2
Z0R/2
R R
VCCO/2 VCCO/2
Z0R/2
R
VCCO/2
Z0R/2
R
VCCO/2
Z0R/2
Virtex-II DCI
2R
2R
VCCO
R
VCCO/2
Z0R/2
Virtex-II DCI
2R
2R
VCCO
Z0R/2
Virtex-II DCI
2R
2R
VCCO
Z0R/2
Virtex-II DCI
2R
2R
VCCO
Virtex-II DCI
R
VCCO VCCO/2
2R
Virtex-II DCI
R
VCCO VCCO/2
2R
Virtex-II DCI
R
VCCO/2
Z0 Z0Z0
Virtex-II DCI
R
VCCO/2
Z02R
2R
2R
Virtex-II DCI
2R
VCCO
Virtex-II DCI
2R
2R
VCCO
Z0
Virtex-II DCIVirtex-II DCI
2R
2R
VCCO
Z0
2R
Virtex-II DCI
2R
VCCO
Virtex-II DCI
2R
2R
VCCO
Z0
Virtex-II DCI
2R
2R
VCCO
Virtex-II DCI
Z0
Virtex-II DCI
2R
2R
VCCO
2R
2R
VCCO
Virtex-II DCI
Z0
Virtex-II DCI
2R
2R
VCCO
2R
2R
VCCO
25Ω(1)
25Ω(1) 25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
25Ω(1)
Notes:1. The SSTL-compatible 25Ω series resistor is accounted for in the DCI buffer, and it is not DCI controlled.2. Z0 is the recommended PCB trace impedance.
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Figure 13 provides examples illustrating the use of the LVDS_DCI and LVDSEXT_DCI I/O standards. For a complete list,see the Virtex-II User Guide.
Figure 13: LVDS DCI Usage Examples
DS031_65c_022103
Conventional
ConventionalTransmitDCI Receive
ReferenceResistor
RecommendedZ0
VRN = VRP = R = Z0
50 Ω
LVDS_DCI and LVDSEXT_DCI Receiver
Virtex-II LVDS DCI
Z0
2R
2R
VCCO
Z0
2R
2R
VCCO
Virtex-II LVDS
Z0
2R
Z0
NOTE: Only LVDS25_DCI is supported (VCCO = 2.5V only)
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Configurable Logic Blocks (CLBs)The Virtex-II configurable logic blocks (CLB) are organizedin an array and are used to build combinatorial and synchro-nous logic designs. Each CLB element is tied to a switchmatrix to access the general routing matrix, as shown inFigure 14. A CLB element comprises 4 similar slices, withfast local feedback within the CLB. The four slices are splitin two columns of two slices with two independent carrylogic chains and one common shift chain.
Slice DescriptionEach slice includes two 4-input function generators, carrylogic, arithmetic logic gates, wide function multiplexers andtwo storage elements. As shown in Figure 15, each 4-inputfunction generator is programmable as a 4-input LUT, 16bits of distributed SelectRAM memory, or a 16-bit vari-able-tap shift register element.
The output from the function generator in each slice drives both the slice output and the D input of the storage element. Figure 16 shows a more detailed view of a single slice.
Configurations
Look-Up Table
Virtex-II function generators are implemented as 4-inputlook-up tables (LUTs). Four independent inputs are pro-vided to each of the two function generators in a slice (F andG). These function generators are each capable of imple-menting any arbitrarily defined boolean function of fourinputs. The propagation delay is therefore independent ofthe function implemented. Signals from the function gener-ators can exit the slice (X or Y output), can input the XORdedicated gate (see arithmetic logic), or input the carry-logicmultiplexer (see fast look-ahead carry logic), or feed the Dinput of the storage element, or go to the MUXF5 (notshown in Figure 16).
In addition to the basic LUTs, the Virtex-II slice containslogic (MUXF5 and MUXFX multiplexers) that combinesfunction generators to provide any function of five, six,seven, or eight inputs. The MUXFX are either MUXF6,MUXF7 or MUXF8 according to the slice considered in theCLB. Selected functions up to nine inputs (MUXF5 multi-plexer) can be implemented in one slice. The MUXFX canalso be a MUXF6, MUXF7, or MUXF8 multiplexers to mapany functions of six, seven, or eight inputs and selectedwide logic functions.
Register/Latch
The storage elements in a Virtex-II slice can be configuredeither as edge-triggered D-type flip-flops or as level-sensi-tive latches. The D input can be directly driven by the X or Youtput via the DX or DY input, or by the slice inputs bypass-ing the function generators via the BX or BY input. The clockenable signal (CE) is active High by default. If left uncon-nected, the clock enable for that storage element defaults tothe active state.
In addition to clock (CK) and clock enable (CE) signals,each slice has set and reset signals (SR and BY sliceinputs). SR forces the storage element into the state speci-fied by the attribute SRHIGH or SRLOW. SRHIGH forces alogic “1” when SR is asserted. SRLOW forces a logic “0”.When SR is used, a second input (BY) forces the storageelement into the opposite state. The reset condition is pre-dominant over the set condition. (See Figure 17.)
The initial state after configuration or global initial state isdefined by a separate INIT0 and INIT1 attribute. By default,setting the SRLOW attribute sets INIT0, and setting theSRHIGH attribute sets INIT1.
For each slice, set and reset can be set to be synchronousor asynchronous. Virtex-II devices also have the ability toset INIT0 and INIT1 independent of SRHIGH and SRLOW.
The control signals clock (CLK), clock enable (CE) andset/reset (SR) are common to both storage elements in oneslice. All of the control signals have independent polarity. Anyinverter placed on a control input is automatically absorbed.
Figure 14: Virtex-II CLB Element
Figure 15: Virtex-II Slice Configuration
SliceX1Y1
SliceX1Y0
SliceX0Y1
SliceX0Y0
FastConnectsto neighbors
SwitchMatrix
DS031_32_101600
SHIFTCIN
COUT
TBUF X0Y1COUT
CIN
TBUF X0Y0
Register
MUXF5
MUXFx
CYSRL16
RAM16
LUTG
Register
Arithmetic Logic
CYLUT
F
DS031_31_100900
SRL16
RAM16
ORCY
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Figure 16: Virtex-II Slice (Top Half)
G4
SOPIN
A4G3 A3G2 A2G1 A1
WG4 WG4WG3 WG3WG2 WG2WG1
BY
WG1
Dual-Port
LUT
FFLATCH
RAMROM
Shift-Reg
D
0
MC15
WS
SR
SR
REV
DI
G
Y
G2
G1BY
10
PROD
D Q
CECECKCLK
MUXCYYB
DIG
DY
Y
0 1
MUXCY0 1
1
SOPOUT
DYMUX
GYMUX
YBMUX
ORCY
WSGWE[2:0]
SHIFTOUT
CYOG
XORG
WECLK
WSF
ALTDIG
CE
SR
CLK
SLICEWE[2:0]
MULTAND
Shared betweenx & y Registers
SHIFTIN COUT
CIN DS031_01_112502
Q
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The set and reset functionality of a register or a latch can beconfigured as follows:
• No set or reset• Synchronous set• Synchronous reset• Synchronous set and reset• Asynchronous set (preset)• Asynchronous reset (clear)• Asynchronous set and reset (preset and clear)
The synchronous reset has precedence over a set, and anasynchronous clear has precedence over a preset.
Distributed SelectRAM Memory
Each function generator (LUT) can implement a 16 x 1-bitsynchronous RAM resource called a distributed SelectRAMelement. The SelectRAM elements are configurable withina CLB to implement the following:
• Single-Port 16 x 8 bit RAM• Single-Port 32 x 4 bit RAM• Single-Port 64 x 2 bit RAM• Single-Port 128 x 1 bit RAM• Dual-Port 16 x 4 bit RAM• Dual-Port 32 x 2 bit RAM• Dual-Port 64 x 1 bit RAM
Distributed SelectRAM memory modules are synchronous(write) resources. The combinatorial read access time isextremely fast, while the synchronous write simplifieshigh-speed designs. A synchronous read can be imple-mented with a storage element in the same slice. The dis-tributed SelectRAM memory and the storage element sharethe same clock input. A Write Enable (WE) input is activeHigh, and is driven by the SR input.
Table 8 shows the number of LUTs (2 per slice) occupied byeach distributed SelectRAM configuration.
For single-port configurations, distributed SelectRAM mem-ory has one address port for synchronous writes and asyn-chronous reads.
For dual-port configurations, distributed SelectRAM mem-ory has one port for synchronous writes and asynchronousreads and another port for asynchronous reads. The func-tion generator (LUT) has separated read address inputs(A1, A2, A3, A4) and write address inputs (WG1/WF1,WG2/WF2, WG3/WF3, WG4/WF4).
In single-port mode, read and write addresses share thesame address bus. In dual-port mode, one function genera-tor (R/W port) is connected with shared read and writeaddresses. The second function generator has the A inputs(read) connected to the second read-only port address andthe W inputs (write) shared with the first read/write portaddress.
Figure 17: Register / Latch Configuration in a Slice
FF
FFY
LATCH
SR REV
D Q
CE
CK
YQ
FF
FFX
LATCH
SR REV
D Q
CE
CK
XQ
CE
DX
DY
BY
CLK
BX
SR
Attribute
INIT1INIT0SRHIGHSRLOW
Attribute
INIT1INIT0SRHIGHSRLOW
Reset TypeSYNCASYNC
DS031_22_110600
Table 8: Distributed SelectRAM Configurations
RAM Number of LUTs
16 x 1S 1
16 x 1D 2
32 x 1S 2
32 x 1D 4
64 x 1S 4
64 x 1D 8
128 x 1S 8
Notes: 1. S = single-port configuration; D = dual-port configuration
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Figure 18, Figure 19, and Figure 20 illustrate various exam-ple configurations.
Similar to the RAM configuration, each function generator(LUT) can implement a 16 x 1-bit ROM. Five configurationsare available: ROM16x1, ROM32x1, ROM64x1,ROM128x1, and ROM256x1. The ROM elements are cas-cadable to implement wider or/and deeper ROM. ROM con-tents are loaded at configuration. Table 9 shows the numberof LUTs occupied by each configuration.
Figure 18: Distributed SelectRAM (RAM16x1S)
Figure 19: Single-Port Distributed SelectRAM (RAM32x1S)
A[3:0]
D
D
DIWS
WSG
WEWCLK
RAM 16x1S
D Q
RAM
WECK
A[4:1]
WG[4:1]
Output
RegisteredOutput
(optional)
(SR)
4
4
(BY)
DS031_02_100900
A[3:0]
D
WSG
F5MUX
WEWCLK
RAM 32x1S
D Q
WEWE0
CKWSF
D
DIWS
RAM
G[4:1]
A[4]
WG[4:1]
D
DIWSRAM
F[4:1]
WF[4:1]
Output
RegisteredOutput
(optional)
(SR)
4
(BY)
(BX)
4
DS031_03_110100
Figure 20: Dual-Port Distributed SelectRAM (RAM16x1D)
Table 9: ROM Configuration
ROM Number of LUTs
16 x 1 1
32 x 1 2
64 x 1 4
128 x 1 8 (1 CLB)
256 x 1 16 (2 CLBs)
A[3:0]
D
WSG
WEWCLK
RAM 16x1D
WECK
D
DIWS
RAMG[4:1]
WG[4:1]
dual_port
RAMdual_port
4
(BY)
DPRA[3:0]
SPO
A[3:0]
WSG
WECK
D
DIWS
G[4:1]
WG[4:1]
DPO4
4
DS031_04_110100
(SR)
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Shift Registers
Each function generator can also be configured as a 16-bitshift register. The write operation is synchronous with aclock input (CLK) and an optional clock enable, as shown inFigure 21. A dynamic read access is performed through the4-bit address bus, A[3:0]. The configurable 16-bit shift regis-ter cannot be set or reset. The read is asynchronous, how-ever the storage element or flip-flop is available toimplement a synchronous read. The storage elementshould always be used with a constant address. For exam-ple, when building an 8-bit shift register and configuring theaddresses to point to the 7th bit, the 8th bit can be theflip-flop. The overall system performance is improved byusing the superior clock-to-out of the flip-flops.
An additional dedicated connection between shift registersallows connecting the last bit of one shift register to the firstbit of the next, without using the ordinary LUT output. (SeeFigure 22.) Longer shift registers can be built with dynamicaccess to any bit in the chain. The shift register chainingand the MUXF5, MUXF6, and MUXF7 multiplexers allow upto a 128-bit shift register with addressable access to beimplemented in one CLB.
Figure 21: Shift Register Configurations
A[3:0]
SHIFTIN
SHIFTOUT
D(BY)
D
MC15
DI
WSG
CE (SR)CLK
SRLC16
D Q
SHIFT-REG
WECK
A[4:1] Output
RegisteredOutput
(optional)
4
DS031_05_110600
WS
Figure 22: Cascadable Shift Register
SRLC16MC15
MC15
D
SRLC16DI
SHIFTIN
CASCADABLE OUT
SLICE S0
SLICE S1
SLICE S2
SLICE S3
1 Shift Chainin CLB
CLB
DS031_06_110200
FF
FFD
SRLC16MC15
MC15
D
SRLC16DI
SHIFTIN
SHIFTOUT
FF
FFD
SRLC16MC15
MC15
D
SRLC16
DI
DI
SHIFTIN
IN
SHIFTOUT
FF
FFD
SRLC16MC15
MC15
D
SRLC16
DI
SHIFTOUT
FF
FFD
DI
DI
DI
OUT
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Multiplexers
Virtex-II function generators and associated multiplexerscan implement the following:
• 4:1 multiplexer in one slice• 8:1 multiplexer in two slices• 16:1 multiplexer in one CLB element (4 slices) • 32:1 multiplexer in two CLB elements (8 slices)
Each Virtex-II slice has one MUXF5 multiplexer and oneMUXFX multiplexer. The MUXFX multiplexer implementsthe MUXF6, MUXF7, or MUXF8, as shown in Figure 23.Each CLB element has two MUXF6 multiplexers, oneMUXF7 multiplexer and one MUXF8 multiplexer. Examplesof multiplexers are shown in the Virtex-II User Guide. AnyLUT can implement a 2:1 multiplexer.
Fast Lookahead Carry Logic
Dedicated carry logic provides fast arithmetic addition andsubtraction. The Virtex-II CLB has two separate carrychains, as shown in the Figure 24.
The height of the carry chains is two bits per slice. The carrychain in the Virtex-II device is running upward. The dedi-cated carry path and carry multiplexer (MUXCY) can also
be used to cascade function generators for implementingwide logic functions.
Arithmetic LogicThe arithmetic logic includes an XOR gate that allows a2-bit full adder to be implemented within a slice. In addition,a dedicated AND (MULT_AND) gate (shown in Figure 16)improves the efficiency of multiplier implementation.
Figure 23: MUXF5 and MUXFX multiplexers
Slice S1
Slice S0
Slice S3
Slice S2
CLB
DS031_08_100201
F5
F6
F5
F7
F5
F6
F5
F8
MUXF8 combines the two MUXF7 outputs (Two CLBs)
MUXF6 combines the two MUXF5 outputs from slices S2 and S3
MUXF7 combines the two MUXF6 outputs from slices S0 and S2
MUXF6 combines the two MUXF5outputs from slices S0 and S1
G
F
G
F
G
F
G
F
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Figure 24: Fast Carry Logic Path
FFLUT
O I MUXCY
FFLUT
O I MUXCY
FFLUT
O I MUXCY
FFLUT
O I MUXCY
CIN
CIN CIN
COUT
FFLUT
O I MUXCY
FFLUT
O I MUXCY
FFLUT
O I MUXCY
FFLUT
O I MUXCY
CIN
COUT
COUTto CIN of S2 of the next CLB
COUTto S0 of the next CLB
(First Carry Chain)
(Second Carry Chain)
SLICE S1
SLICE S0
SLICE S3
SLICE S2
CLB
DS031_07_110200
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Sum of ProductsEach Virtex-II slice has a dedicated OR gate named ORCY,ORing together outputs from the slices carryout and the ORCYfrom an adjacent slice. The ORCY gate with the dedicatedSum of Products (SOP) chain are designed for implementinglarge, flexible SOP chains. One input of each ORCY is con-nected through the fast SOP chain to the output of the previousORCY in the same slice row. The second input is connected tothe output of the top MUXCY in the same slice, as shown inFigure 25.
LUTs and MUXCYs can implement large AND gates orother combinatorial logic functions. Figure 26 illustratesLUT and MUXCY resources configured as a 16-input ANDgate.
Figure 25: Horizontal Cascade Chain
MUXCY4
MUXCY4
Slice 1
ds031_64_110300
ORCY
LUT
LUT
MUXCY4
MUXCY4
Slice 0
VCC
LUT
LUT
MUXCY4
MUXCY4
Slice 3
ORCY
LUT
LUT
MUXCY4
MUXCY4
Slice 2
VCC
LUT
LUT
SOP
CLB
MUXCY4
MUXCY4
Slice 1
ORCY
LUT
LUT
MUXCY4
MUXCY4
Slice 0
VCC
LUT
LUT
MUXCY4
MUXCY4
Slice 3
ORCY
LUT
LUT
MUXCY4
MUXCY4
Slice 2
VCC
LUT
LUT
CLB
Figure 26: Wide-Input AND Gate (16 Inputs)
MUXCY
AND
4
16
MUXCY4
“0”
0 1
0 1
“0”
0 1
“0”
MUXCY4
Slice
OUT
OUT
Slice
LUT
DS031_41_110600
LUT
LUT
VCC
MUXCY4
0 1LUT
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3-State Buffers
IntroductionEach Virtex-II CLB contains two 3-state drivers (TBUFs)that can drive on-chip busses. Each 3-state buffer has itsown 3-state control pin and its own input pin.
Each of the four slices have access to the two 3-state buff-ers through the switch matrix, as shown in Figure 27.TBUFs in neighboring CLBs can access slice outputs bydirect connects. The outputs of the 3-state buffers drive hor-izontal routing resources used to implement 3-state busses.
The 3-state buffer logic is implemented using AND-OR logicrather than 3-state drivers, so that timing is more predict-able and less load dependant especially with larger devices.
Locations / OrganizationFour horizontal routing resources per CLB are provided foron-chip 3-state busses. Each 3-state buffer has accessalternately to two horizontal lines, which can be partitionedas shown in Figure 28. The switch matrices correspondingto SelectRAM memory and multiplier or I/O blocks areskipped.
Number of 3-State BuffersTable 10 shows the number of 3-state buffers available ineach Virtex-II device. The number of 3-state buffers is twicethe number of CLB elements.
CLB/Slice Configurations
Table 11 summarizes the logic resources in one CLB. All of the CLBs are identical and each CLB or slice can beimplemented in one of the configurations listed. Table 12 shows the available resources in all CLBs.
Figure 27: Virtex-II 3-State Buffers
SliceS3
SliceS2
SliceS1
SliceS0
SwitchMatrix
DS031_37_060700
TBUF
TBUF
Table 10: Virtex-II 3-State Buffers
Device3-State Buffers
per RowTotal Number
of 3-State Buffers
XC2V40 16 128
XC2V80 16 256
XC2V250 32 768
XC2V500 48 1,536
XC2V1000 64 2,560
XC2V1500 80 3,840
XC2V2000 96 5,376
XC2V3000 112 7,168
XC2V4000 144 11,520
XC2V6000 176 16,896
XC2V8000 208 23,296
Figure 28: 3-State Buffer Connection to Horizontal Lines
SwitchmatrixCLB-II
SwitchmatrixCLB-II
DS031_09_032700
Programmableconnection
3 - state lines
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18 Kbit Block SelectRAM Resources
IntroductionVirtex-II devices incorporate large amounts of 18 Kbit blockSelectRAM. These complement the distributed SelectRAMresources that provide shallow RAM structures imple-mented in CLBs. Each Virtex-II block SelectRAM is an 18Kbit true dual-port RAM with two independently clocked andindependently controlled synchronous ports that access acommon storage area. Both ports are functionally identical.CLK, EN, WE, and SSR polarities are defined through con-figuration.
Each port has the following types of inputs: Clock and ClockEnable, Write Enable, Set/Reset, and Address, as well asseparate Data/parity data inputs (for write) and Data/paritydata outputs (for read).
Operation is synchronous; the block SelectRAM behaveslike a register. Control, address and data inputs must (andneed only) be valid during the set-up time window prior to a
rising (or falling, a configuration option) clock edge. Dataoutputs change as a result of the same clock edge.
ConfigurationThe Virtex-II block SelectRAM supports various configura-tions, including single- and dual-port RAM and variousdata/address aspect ratios. Supported memory configura-tions for single- and dual-port modes are shown in Table 13.
Table 11: Logic Resources in One CLB
Slices LUTs Flip-Flops MULT_ANDsArithmetic & Carry-Chains
SOP Chains
Distributed SelectRAM
Shift Registers TBUF
4 8 8 8 2 2 128 bits 128 bits 2
Table 12: Virtex-II Logic Resources Available in All CLBs
Device
CLB Array: Row x
Column
Number of
Slices
Number of
LUTs
Max Distributed SelectRAM or Shift
Register (bits)
Number of
Flip-Flops
Number of
Carry-Chains(1)
Number of SOP
Chains(1)
XC2V40 8 x 8 256 512 8,192 512 16 16
XC2V80 16 x 8 512 1,024 16,384 1,024 16 32
XC2V250 24 x 16 1,536 3,072 49,152 3,072 32 48
XC2V500 32 x 24 3,072 6,144 98,304 6,144 48 64
XC2V1000 40 x 32 5,120 10,240 163,840 10,240 64 80
XC2V1500 48 x 40 7,680 15,360 245,760 15,360 80 96
XC2V2000 56 x 48 10,752 21,504 344,064 21,504 96 112
XC2V3000 64 x 56 14,336 28,672 458,752 28,672 112 128
XC2V4000 80 x 72 23,040 46,080 737,280 46,080 144 160
XC2V6000 96 x 88 33,792 67,584 1,081,344 67,584 176 192
XC2V8000 112 x 104 46,592 93,184 1,490,944 93,184 208 224
Notes: 1. The carry-chains and SOP chains can be split or cascaded.
Table 13: Dual- and Single-Port Configurations
16K x 1 bit 2K x 9 bits
8K x 2 bits 1K x 18 bits
4K x 4 bits 512 x 36 bits
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Single-Port Configuration
As a single-port RAM, the block SelectRAM has access tothe 18 Kbit memory locations in any of the 2K x 9-bit,1K x 18-bit, or 512 x 36-bit configurations and to 16 Kbitmemory locations in any of the 16K x 1-bit, 8K x 2-bit, or4K x 4-bit configurations. The advantage of the 9-bit, 18-bitand 36-bit widths is the ability to store a parity bit for eacheight bits. Parity bits must be generated or checked exter-nally in user logic. In such cases, the width is viewed as 8 +1, 16 + 2, or 32 + 4. These extra parity bits are stored andbehave exactly as the other bits, including the timing param-eters. Video applications can use the 9-bit ratio of Virtex-IIblock SelectRAM memory to advantage.
Each block SelectRAM cell is a fully synchronous memoryas illustrated in Figure 29. Input data bus and output databus widths are identical.
Dual-Port Configuration
As a dual-port RAM, each port of block SelectRAM hasaccess to a common 18 Kbit memory resource. These arefully synchronous ports with independent control signals foreach port. The data widths of the two ports can be config-ured independently, providing built-in bus-width conversion.
Table 14 illustrates the different configurations available onports A & B.
If both ports are configured in either 2K x 9-bit, 1K x 18-bit,or 512 x 36-bit configurations, the 18 Kbit block is accessi-ble from port A or B. If both ports are configured in either16K x 1-bit, 8K x 2-bit. or 4K x 4-bit configurations, the
16 K-bit block is accessible from Port A or Port B. All otherconfigurations result in one port having access to an 18 Kbitmemory block and the other port having access to a 16 K-bitsubset of the memory block equal to 16 Kbits.
Figure 29: 18 Kbit Block SelectRAM Memory in Single-Port Mode
DOP
DIP
ADDR
WE
ENSSR
CLK
18 Kbit Block SelectRAM
DS031_10_071602
DI
DO
Table 14: Dual-Port Mode Configurations
Port A 16K x 1 16K x 1 16K x 1 16K x 1 16K x 1 16K x 1
Port B 16K x 1 8K x 2 4K x 4 2K x 9 1K x 18 512 x 36
Port A 8K x 2 8K x 2 8K x 2 8K x 2 8K x 2
Port B 8K x 2 4K x 4 2K x 9 1K x 18 512 x 36
Port A 4K x 4 4K x 4 4K x 4 4K x 4
Port B 4K x 4 2K x 9 1K x 18 512 x 36
Port A 2K x 9 2K x 9 2K x 9
Port B 2K x 9 1K x 18 512 x 36
Port A 1K x 18 1K x 18
Port B 1K x 18 512 x 36
Port A 512 x 36
Port B 512 x 36
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Each block SelectRAM cell is a fully synchronous memory,as illustrated in Figure 30. The two ports have independentinputs and outputs and are independently clocked.
Port Aspect RatiosTable 15 shows the depth and the width aspect ratios for the18 Kbit block SelectRAM. Virtex-II block SelectRAM alsoincludes dedicated routing resources to provide an efficientinterface with CLBs, block SelectRAM, and multipliers.
Read/Write OperationsThe Virtex-II block SelectRAM read operation is fully syn-chronous. An address is presented, and the read operationis enabled by control signals WEA and WEB in addition toENA or ENB. Then, depending on clock polarity, a rising orfalling clock edge causes the stored data to be loaded intooutput registers.
The write operation is also fully synchronous. Data andaddress are presented, and the write operation is enabledby control signals WEA or WEB in addition to ENA or ENB.Then, again depending on the clock input mode, a rising orfalling clock edge causes the data to be loaded into thememory cell addressed.
A write operation performs a simultaneous read operation.Three different options are available, selected by configura-tion:
1. “WRITE_FIRST”
The “WRITE_FIRST” option is a transparent mode. The same clock edge that writes the data input (DI) into the memory also transfers DI into the output registers DO as shown in Figure 31.
Figure 30: 18 Kbit Block SelectRAM in Dual-Port Mode
DOPA
DOPB
DIPA
ADDRA
WEA
ENASSRA
CLKA
DIPB
ADDRB
WEB
ENBSSRB
CLKB
18 Kbit Block SelectRAM
DS031_11_071602
DOB
DOA
DIA
DIB
Table 15: 18 Kbit Block SelectRAM Port Aspect Ratio
Width Depth Address Bus Data Bus Parity Bus
1 16,384 ADDR[13:0] DATA[0] N/A
2 8,192 ADDR[12:0] DATA[1:0] N/A
4 4,096 ADDR[11:0] DATA[3:0] N/A
9 2,048 ADDR[10:0] DATA[7:0] Parity[0]
18 1,024 ADDR[9:0] DATA[15:0] Parity[1:0]
36 512 ADDR[8:0] DATA[31:0] Parity[3:0]
Figure 31: WRITE_FIRST Mode
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2. “READ_FIRST”
The “READ_FIRST” option is a read-before-write mode.
The same clock edge that writes data input (DI) into the memory also transfers the prior content of the memory celladdressed into the data output registers DO, as shown in Figure 32.
3. “NO_CHANGE”
The “NO_CHANGE” option maintains the content of the output registers, regardless of the write operation. The clock edgeduring the write mode has no effect on the content of the data output register DO. When the port is configured as“NO_CHANGE”, only a read operation loads a new value in the output register DO, as shown in Figure 33.
Figure 32: READ_FIRST Mode
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Figure 33: NO_CHANGE Mode
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Control Pins and AttributesVirtex-II SelectRAM memory has two independent portswith the control signals described in Table 16. All controlinputs including the clock have an optional inversion.
Initial memory content is determined by the INIT_xxattributes. Separate attributes determine the output registervalue after device configuration (INIT) and SSR is asserted(SRVAL). Both attributes (INIT_B and SRVAL) are availablefor each port when a block SelectRAM resource is config-ured as dual-port RAM.
LocationsVirtex-II SelectRAM memory blocks are located in eitherfour or six columns. The number of blocks per columndepends of the device array size and is equivalent to the
number of CLBs in a column divided by four. Column loca-tions are shown in Table 17.
Table 16: Control Functions
Control Signal Function
CLK Read and Write Clock
EN Enable affects Read, Write, Set, Reset
WE Write Enable
SSR Set DO register to SRVAL (attribute)
Table 17: SelectRAM Memory Floor Plan
Device Columns
SelectRAM Blocks
Per Column Total
XC2V40 2 2 4
XC2V80 2 4 8
XC2V250 4 6 24
XC2V500 4 8 32
XC2V1000 4 10 40
XC2V1500 4 12 48
XC2V2000 4 14 56
XC2V3000 6 16 96
XC2V4000 6 20 120
XC2V6000 6 24 144
XC2V8000 6 28 168
Figure 34: Block SelectRAM (2-column, 4-column, and 6-column)
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Total Amount of SelectRAM Memory
Table 18 shows the amount of block SelectRAM memoryavailable for each Virtex-II device. The 18 Kbit SelectRAMblocks are cascadable to implement deeper or wider single- ordual-port memory resources.
18-Bit x 18-Bit Multipliers
IntroductionA Virtex-II multiplier block is an 18-bit by 18-bit 2’s comple-ment signed multiplier. Virtex-II devices incorporate manyembedded multiplier blocks. These multipliers can be asso-ciated with an 18 Kbit block SelectRAM resource or can beused independently. They are optimized for high-speedoperations and have a lower power consumption comparedto an 18-bit x 18-bit multiplier in slices.
Each SelectRAM memory and multiplier block is tied to fourswitch matrices, as shown in Figure 35.
Association With Block SelectRAM MemoryThe interconnect is designed to allow SelectRAM memoryand multiplier blocks to be used at the same time, but someinterconnect is shared between the SelectRAM and themultiplier. Thus, SelectRAM memory can be used only up to18 bits wide when the multiplier is used, because the multi-plier shares inputs with the upper data bits of theSelectRAM memory.
This sharing of the interconnect is optimized for an18-bit-wide block SelectRAM resource feeding the multi-plier. The use of SelectRAM memory and the multiplier withan accumulator in LUTs allows for implementation of a digi-tal signal processor (DSP) multiplier-accumulator (MAC)function, which is commonly used in finite and infiniteimpulse response (FIR and IIR) digital filters.
ConfigurationThe multiplier block is an 18-bit by 18-bit signed multiplier(2's complement). Both A and B are 18-bit-wide inputs, andthe output is 36 bits. Figure 36 shows a multiplier block.
Table 18: Virtex-II SelectRAM Memory Available
Device
Total SelectRAM Memory
Blocks in Kbits in Bits
XC2V40 4 72 73,728
XC2V80 8 144 147,456
XC2V250 24 432 442,368
XC2V500 32 576 589,824
XC2V1000 40 720 737,280
XC2V1500 48 864 884,736
XC2V2000 56 1,008 1,032,192
XC2V3000 96 1,728 1,769,472
XC2V4000 120 2,160 2,211,840
XC2V6000 144 2,592 2,654,208
XC2V8000 168 3,024 3,096,576
Figure 35: SelectRAM and Multiplier Blocks
Figure 36: Multiplier Block
SwitchMatrix
SwitchMatrix
18-Kbit blockSelectRAM
18 x
18
Mul
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Locations / OrganizationMultiplier organization is identical to the 18 Kbit SelectRAMorganization, because each multiplier is associated with an18 Kbit block SelectRAM resource.
In addition to the built-in multiplier blocks, the CLB elementshave dedicated logic to implement efficient multipliers inlogic. (Refer to Configurable Logic Blocks (CLBs)).
Table 19: Multiplier Floor Plan
Device Columns
Multipliers
Per Column Total
XC2V40 2 2 4
XC2V80 2 4 8
XC2V250 4 6 24
XC2V500 4 8 32
XC2V1000 4 10 40
XC2V1500 4 12 48
XC2V2000 4 14 56
XC2V3000 6 16 96
XC2V4000 6 20 120
XC2V6000 6 24 144
XC2V8000 6 28 168
Figure 37: Multipliers (2-column, 4-column, and 6-column)
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Global Clock Multiplexer BuffersVirtex-II devices have 16 clock input pins that can also beused as regular user I/Os. Eight clock pads are on the topedge of the device, in the middle of the array, and eight areon the bottom edge, as illustrated in Figure 38.
The global clock multiplexer buffer represents the input todedicated low-skew clock tree distribution in Virtex-IIdevices. Like the clock pads, eight global clock multiplexerbuffers are on the top edge of the device and eight are onthe bottom edge.
Each global clock buffer can either be driven by the clockpad to distribute a clock directly to the device, or driven bythe Digital Clock Manager (DCM), discussed in DigitalClock Manager (DCM), page 30. Each global clock buffer
can also be driven by local inte