Stratix V Device Design Guidelines

Stratix V Device Design Guidelines
Stratix V Device Design Guidelines
AN-625-1.1
Application Note
This application note provides a set of design guidelines, recommendations, and a list
of factors to consider for designs that use Altera® Stratix® V FPGAs. It is important to
follow Altera recommendations throughout the design process for high-density,
high-performance Stratix V designs. This document also assists you with planning the
FPGA and system early in the design process, which is crucial to successfully meet
design requirements. You can use the “Design Checklist” on page 53 to help verify
that you have followed each of the guidelines.
f This application note does not include all Stratix V device details and features. For
more information about Stratix V devices and features, refer to the Stratix V Device
Handbook.
The material references the Stratix V device architecture as well as aspects of the
Quartus® II software and third-party tools that you might use in your design. The
guidelines presented in this document can improve productivity and avoid common
design pitfalls. Table 1 shows the stages in the design flow and contains a brief
description of the guidelines covered in each stage.
Table 1. Summary of the Design Flow Stage and Guideline Topics
Stages of the Design Flow
Guidelines
“System Specification” on page 2
Planning design specifications, IP selection
“Device Selection” on page 4
Device information, determining device variant and density, package offerings,
migration, HardCopy ASICs, speed grade
“Early System and Board Planning” on
page 8
Early power estimation, thermal management option, planning for configuration
scheme, planning for on-chip debugging
“Pin Connection Considerations for
Board Design” on page 16
Power-up, power pins, PLL connections, decoupling capacitors, configuration
pins, signal integrity, board-level verification
“I/O and Clock Planning” on page 25
Pin assignments, early pin planning, I/O features and connections, memory
interfaces, clock and PLL selection, simultaneous switching noise (SSN)
“Design Entry” on page 37
Coding styles and design recommendations, SOPC Builder, planning for
hierarchical or team-based design
“Design Implementation, Analysis,
Optimization, and Verification” on
page 43
Synthesis tool, device utilization, messages, timing constraints and analysis, area
and timing optimization, compilation time, verification, power analysis and
optimization
f For complete details about the Stratix V device architecture, refer to the Stratix V
Literature page. For the latest known issues related to Stratix V FPGAs, refer to the
Knowledge Database.
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December 2013
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Page 2
System Specification
Figure 1 shows the various stages of the design flow in the order that each stage is
typically performed.
Figure 1. Stratix V Device Design Flow
Start
System Specification
Design Specification
IP Selection
Device Selection
Early HDL Development
Considerations for HDL and
Board Development
Early System and Board Planning
Start SOPC Builder/HDL
Design with Avalon Bus
Configuration
Power
Clock and PLL
Selection
Debugging Capability
Thermal
Nios II
Signal Integrity
Decoupling
Dynamic Reconfiguration
I/O Features and
Pin Connections
Layout
Design Implementation
Memory Interfaces
Timing Constraints
and Analysis
Simulation
Design Verification
End
System Specification
In systems that contain a Stratix V device, the FPGA typically plays a large role in the
overall system and affects the rest of the system design. It is important to start the
design process by creating detailed design specifications for the system and the
FPGA, and determining the FPGA input and output interfaces to the rest of the
system.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
System Specification
Page 3
Design Specifications
Create detailed design specifications that define the system before you create your
logic design or complete your system design, by performing the following:
■
Specify the I/O interfaces for the FPGA
■
Identify the different clock domains
■
Include a block diagram of basic design functions
■
Include intellectual property (IP) blocks
For suggestions about including intellectual property blocks, refer to “IP
Selection”. Taking the time to create these specifications improves design
efficiency, but this stage is often skipped by FPGA designers.
■
Create a functional verification/test plan
■
Consider a common design directory structure
1. Create detailed design specifications and a test plan if appropriate.
2. Plan clock domains, clock resources, and I/O interfaces early with a block diagram.
Create a functional verification plan to ensure the team knows how to verify the
system. Creating a test plan at this stage can also help you design for testability and
design for manufacturability. For example, do you want to perform built-in-self test
(BIST) functions to drive interfaces? If so, you could use a UART interface with a
Nios® II processor inside the FPGA device. You might require the ability to validate all
the design interfaces. Refer to “Planning for On-Chip Debugging” on page 15 for
guidelines related to analyzing and debugging the device after it is in the system.
If your design includes multiple designers, it is useful to consider a common design
directory structure. This eases the design integration stages. “Planning for
Hierarchical and Team-Based Design” on page 41 provides more suggestions for
team-based designs.
IP Selection
Altera and its third-party IP partners offer a large selection of off-the-shelf IP cores
optimized for Altera devices. You can easily implement these parameterized blocks of
IP in your design, reducing your system implementation and verification time, and
allowing you to concentrate on adding proprietary value.
3. Select IP that affects system design, especially I/O interfaces.
4.
If you plan to use the OpenCore Plus tethered mode for IP, ensure that your board design supports
this mode of operation.
IP selection often affects system design, especially if the FPGA interfaces with other
devices in the system. Consider which I/O interfaces or other blocks in your system
design can be implemented using IP cores, and plan to incorporate these cores in your
FPGA design.
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Stratix V Device Design Guidelines
Page 4
Device Selection
The OpenCore Plus feature available for many IP cores allows you to program the
FPGA to verify your design in hardware before you purchase the IP license. The
evaluation supports an untethered mode, in which the design runs for a limited time,
or a tethered mode. The tethered mode requires an Altera serial JTAG cable connected
between the JTAG port on your board and a host computer running the Quartus II
Programmer for the duration of the hardware evaluation period.
f For descriptions of available IP cores, refer to the Intellectual Property page under
Products on Altera’s website at www.altera.com.
SOPC Builder
The SOPC Builder is a system development tool you can use to create systems based
on processors, peripherals, and memories. With the SOPC Builder, you specify the
system components in a GUI, and the SOPC Builder generates the interconnect logic
automatically. The SOPC Builder outputs HDL files that define all components of the
system, and a top-level HDL design file that connects all the components together.
The SOPC Builder is a general purpose tool for creating SOPC designs that may or
may not contain a processor. SOPC Builder components use Avalon interfaces for the
physical connection of components, and you can use the SOPC Builder to connect any
logical device (either on-chip or off-chip) that has an Avalon interface. The Avalon
Memory-Mapped interface allows a component to use an address mapped read/write
protocol that enables flexible topologies for connecting master components to any
slave components. The Avalon Streaming interface enables point-to-point connections
between streaming components that send and receive data using a high-speed,
unidirectional system interconnect between the source and sink ports.
5. Take advantage of the SOPC Builder for system and processor designs.
f For more information about the Avalon interface, refer to the Avalon Interface
Specifications manual.
f For information about using the SOPC Builder to improve your productivity, refer to
the SOPC Builder Literature page on the Altera website.
Device Selection
This section describes the first step in the Stratix V design process—choosing the
device family variant, device density, features, package, and speed grade that best suit
your design requirements. You should also consider whether you want to target
FPGA or HardCopy ASIC migration devices (also described in this section).
6.
Select a device based on transceivers, I/O pin count, LVDS channels, package offering,
logic/memory/multiplier density, PLLs, clock routing, and speed grade.
f For more information about the features available in each device density, including
logic, memory blocks, multipliers, and phase-locked loops (PLLs), as well as the
various package offerings and I/O pin counts, refer to the Stratix V Device Family
Overview.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Device Selection
Page 5
Device Family Variant and High-Speed Transceivers
The Stratix V device family currently contains two variants optimized to meet
different application requirements. Both transceiver-based device variants contain
full-duplex clock data recovery (CDR)-based transceivers at up to 12.5 Gbps.
Stratix V GS devices have transceivers on one side of the device, while Stratix V GX
devices have transceivers on two sides.
For information about transceiver board design guidelines, refer to “Appendix:
Stratix V Transceiver Design Guidelines” on page 59.
Logic, Memory, and Multiplier Density
Stratix V devices offer a range of densities that provide different amounts of device
logic resources, including memory, multipliers, and adaptive logic module (ALM)
logic cells. Determining the required logic density can be a challenging part of the
design planning process. Devices with more logic resources can implement larger and
potentially more complex designs, but generally have a higher cost. Smaller devices
have lower static power utilization. Stratix V devices support vertical migration,
which provides flexibility, as described in “Vertical Device Migration” on page 6.
Many next-generation designs use a current design as a starting point. If you have
other designs that target an Altera device, you can use their resource utilization as an
estimate for your new design. Review the resource utilization to find out which
device density fits the design. Consider that the coding style, device architecture, and
optimization options used in the Quartus II software can significantly affect a design’s
resource utilization and timing performance. For more information about
determining resource utilization for a compiled design, refer to “Device Resource
Utilization Reports” on page 43.
7. Reserve device resources for future development and debugging.
f To obtain resource utilization estimates for certain configurations of Altera’s IP
designs, refer to the user guides for Altera megafunctions and IP MegaCores on the IP
Megafunctions page in the Literature section at www.altera.com.
Select a device that meets your design requirements with some safety margin in case
you want to add more logic later in the design cycle, upgrade, or expand your design.
You might also want additional space in the device to ease design floorplan creation
for an incremental or team-based design, as described in “Planning for Hierarchical
and Team-Based Design” on page 41. Consider reserving resources for debugging, as
described in “Planning for On-Chip Debugging” on page 15.
I/O Pin Count, LVDS Channels, and Package Offering
Stratix V devices are available in space-saving FineLine BGA packages with various
I/O pin counts between 264 and 1,032 user I/O pins. Determine the required number
of I/O pins for your application, considering the design’s interface requirements with
other system blocks.
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Stratix V Device Design Guidelines
Page 6
Device Selection
Larger densities and package pin counts offer more full-duplex LVDS channels for
different signaling; ensure that your device density-package combination includes
enough LVDS channels. Other factors can also affect the number of I/O pins required
for a design, including simultaneous switching noise (SSN) concerns, pin placement
guidelines, pins used as dedicated inputs, I/O standard availability for each I/O
bank, differences between I/O standards and speed for row and column I/O banks,
and package migration options. For more details about choosing pin locations, refer to
“Pin Connection Considerations for Board Design” on page 16, and “I/O and Clock
Planning” on page 25.
You can compile any existing designs in the Quartus II software to determine how
many I/O pins are used. Also consider reserving I/O pins for debugging, as
described in “Planning for On-Chip Debugging” on page 15.
PLLs and Clock Routing
Stratix V devices include up to 24 fractional PLLs (with additional PLLs available
from unused transceivers). There are up to 16 global clocks (GCLKs), 92 regional
clocks (RCLKs), and 309 periphery clocks (PCLKs). Verify that your chosen device
density package combination includes enough PLLs and clock routing resources for
your design.
GCLK resources are shared between certain PLLs, which can affect which inputs are
available for use. For more details and references regarding clock pins and global
routing resources, refer to “I/O and Clock Planning” on page 25.
Speed Grade
The device speed grade affects the device timing performance and timing closure, as
well as power utilization. Stratix V devices are available in three speed grades: -2, -3,
and -4 (-2 is the fastest). One way to determine which speed grade your design
requires is to consider the supported clock rates for specific I/O interfaces.
f For information about supported clock rates for memory interfaces using I/O pins on
different sides of the device in different device speed grades, refer to the External
Memory Interfaces in Stratix V Devices chapter in volume 1 of the Stratix V Device
Handbook.
1
Some designers use the fastest speed grade during prototyping to reduce compilation
time (because less time is spent optimizing the design to meet timing requirements),
and then move to a slower speed grade for production to reduce cost if the design
meets its timing requirements.
Vertical Device Migration
Stratix V devices support vertical migration within the same package, which enables
you to migrate to different density devices whose dedicated input pins, configuration
pins, and power pins are the same for a given package. This feature allows future
upgrades or changes to your design without any changes to the board layout, because
you can replace the FPGA on the board with a different density Stratix V device.
8. Consider vertical device migration availability and requirements.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Device Selection
Page 7
Determine whether you want the option of migrating your design to another device
density. Choose your device density and package to accommodate any possible future
device migration to allow flexibility when the design nears completion. You should
specify any potential migration options in the Quartus II software at the beginning of
your design cycle or as soon as the device migration selection is possible in the
Quartus II software. Selecting a migration device can impact the design’s pin
placement, because the Fitter ensures your design is compatible with the selected
device(s). It is possible to add migration devices later in the design cycle, but it
requires extra effort to check pin assignments, and can require design or board layout
changes to fit into the new target device. It is easier to consider these issues early in
the design cycle than at the end, when the design is near completion and ready for
migration.
As described in “Making FPGA Pin Assignments” on page 26, the Quartus II Pin
Planner highlights pins that change function in the migration device when compared
to the currently selected device.
HardCopy V ASIC Migration
The HardCopy methodology allows you to seamlessly prototype your system with
Stratix V FPGAs, and completely prepares your system for production prior to ASIC
design handoff. Altera’s HardCopy Design Center uses a proven turnkey process to
implement the low-cost, low power, functionally equivalent, pin-compatible
HardCopy V ASIC.
You can start your HardCopy V ASIC design by targeting your design to an
appropriate Stratix V FPGA and choosing the appropriate HardCopy V ASIC
companion in the latest version of the Quartus II software or as soon as the selection is
possible in the Quartus II software. You can migrate between the FPGA and ASIC
revisions of your project when the Quartus II software includes these devices.
9. If you want to migrate to a HardCopy V ASIC, review the appropriate design considerations.
Review the HardCopy guidelines early in the design cycle for any Quartus II software
settings that you should use or other restrictions you should consider as you complete
your design. For example:
■
Use complete timing constraints if you want to migrate to a HardCopy device
because of the rigorous verification requirements for ASICs.
■
RAM cannot be initialized to a known value in the HardCopy ASIC as it can in an
FPGA. Therefore, your design must write RAM contents during device operation
instead of relying on memory initialization values.
In addition, review the HardCopy Readiness Report that is generated during
compilation when a HardCopy companion device is selected in the Device Settings
dialog box. This advises you about any incomplete I/O assignments and provides
recommendations for clock pin locations.
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Stratix V Device Design Guidelines
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Early System and Board Planning
Early System and Board Planning
System information related to the FPGA should be planned early in the design
process, before designers have completed the design in the Quartus II software. Early
planning allows the FPGA team to provide early information to PCB board and
system designers. This section includes the following topics:
■
“Early Power Estimation”
■
“Temperature Sensing for Thermal Management” on page 9
■
“Planning for Device Configuration” on page 10
■
“Planning for On-Chip Debugging” on page 15
Early Power Estimation
FPGA power consumption is an important design consideration and must be
estimated accurately to develop an appropriate power budget to design the power
supplies, voltage regulators, decouplers, heat sink, and cooling system. Power
estimation and analysis have two significant planning requirements:
10.
■
Thermal planning—The cooling solution must sufficiently dissipate the heat
generated by the device. In particular, the computed junction temperature must
fall within normal device specifications.
■
Power supply planning—The power supplies must provide adequate current to
support device operation.
Estimate power consumption with the PowerPlay Early Power Estimator (EPE) spreadsheet to plan the
cooling solution and power supplies before the logic design is complete.
Power consumption in FPGA devices is dependent on the logic design. This
dependence can make power estimation challenging during the early board
specification and layout stages. The Altera PowerPlay EPE spreadsheet allows you to
estimate power utilization before the design is complete by processing information
about the device and the device resources that will be used in the design, as well as
the operating frequency, toggle rates, and environmental considerations. You can use
the spreadsheet to calculate the device junction temperature by entering the ambient
temperature, along with information about the heat sinks, air flow, and board thermal
model. The EPE then calculates the power, current estimates, and thermal analysis for
the design.
If you do not have an existing design, estimate the number of device resources used in
your design and enter it manually. The spreadsheet accuracy depends on your inputs
and your estimation of the device resources. If this information changes (during or
after your design is complete), your power estimation results are less accurate. If you
have an existing design or a partially-completed compiled design, use the Generate
PowerPlay Early Power Estimator File command in the Quartus II software to
provide input to the spreadsheet.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Early System and Board Planning
Page 9
The PowerPlay EPE spreadsheet includes the Import Data macro, which parses the
information in the Quartus II generated power estimation file, or alternatively from
an older version of the EPE, and transfers it into the spreadsheet. If you do not want to
use the macro, you can transfer the data into the EPE spreadsheet manually. You
should enter additional resources to be used in the final design manually if the
existing Quartus II project represents only a portion of your full design. You can edit
the spreadsheet and add additional device resources or adjust the parameters after
importing the power estimation file information.
When the design is complete, the PowerPlay Power Analyzer tool in the Quartus II
software provides an accurate estimation of power, ensuring that thermal and supply
budgets are not violated. For the most accurate power estimation, use gate-level
simulation results with an output file (.vcd) output file from a third-party simulation
tool. Refer to “Power Analysis” on page 49.
f The PowerPlay EPE spreadsheets and user guides for each supported device family
are available on the Altera website at:
www.altera.com/support/devices/estimator/pow-powerplay.html
f For more information about using the EPE spreadsheet, refer to the PowerPlay Early
Power Estimator User Guide. For more information about power estimation and
analysis, refer to the PowerPlay Power Analysis chapter in volume 3 of the Quartus II
Handbook.
Temperature Sensing for Thermal Management
Calculating or measuring the junction temperature is crucial for thermal
management. Historically, junction temperature is calculated using ambient or case
temperature, junction-to-ambient (JA) or junction to case (JC) thermal resistance,
and the device power consumption. Stratix V devices include a temperature sensing
diode (TSD) with embedded analog-to-digital converter (ADC) circuitry, so you do
not require an external temperature sensing chip on the board.
11.
Set up the temperature sensing diode in your design to measure the device junction temperature for
thermal management.
The Stratix V TSD can self-monitor the device junction temperature and be used with
external circuitry for activities such as controlling air flow to the FPGA. You can
bypass the ADC if you want to use an external temperature sensor, similar to the
solution used for a Stratix II device or other devices.
You must include the TSD circuitry in your design if you want to use it. Ensure you
make the correct external pin connections, whether you use both the ADC and TSD,
or bypass the ADC and connect the sensing diode to an external temperature sensor.
f For more information about these features, refer to the Power Management in Stratix V
Devices chapter in volume 1 of the Stratix V Device Handbook.
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Stratix V Device Design Guidelines
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Early System and Board Planning
Planning for Device Configuration
Stratix V devices are based on SRAM cells, so you must download configuration data
to the Stratix V device each time the device powers up, because SRAM memory is
volatile. Consider whether you require multiple configuration schemes, such as one
for debugging or testing and another for the production environment.
Choosing the device configuration method early allows system and board designers
to determine what companion devices, if any, are required for the system. Your board
layout also depends on the configuration method you plan to use for the
programmable device, because different schemes require different connections. For
board design guidelines related to configuration pins and connecting devices for
configuration, refer to “Pin Connection Considerations for Board Design” on page 16.
In addition, Stratix V devices offer advanced configuration features, depending on
your configuration scheme. Stratix V devices also include optional configuration pins
and a reconfiguration option that you should choose early in the design process (and
set up in the Quartus II software), so you have all the information required for your
board and system design.
This section includes the following topics:
■
“Configuration Scheme Selection” on page 10
■
“Configuration Features” on page 12
■
“Quartus II Configuration Settings” on page 14
f For more information about configuration, refer to the Configuration, Design Security,
Remote System Upgrades with Stratix V Devices chapter in volume 1 of the Stratix V
Device Handbook. For more information, refer to the Configuration Center. This web
page includes links to JTAG Configuration & ISP Troubleshooter and FPGA
Configuration Troubleshooter that you can use to help debug configuration problems.
Configuration Scheme Selection
You can configure Stratix V devices with one of four configuration schemes:
■
Fast passive parallel (FPP)—A controller supplies the configuration data in a
parallel manner to the Stratix V FPGA. FPP is supported in an 8-bit (FPP ×8), 16-bit
(FPP ×16) or 32-bit data width (FPP ×32).
■
Active serial (AS)—The Stratix V FPGA controls the configuration process and
gets the configuration data from a serial configuration (EPCS) device or from a
qual-serial configuration (EPCS) device. AS is supported in 1-bit (AS ×1) or 4-bit
data width (AS ×4).
■
Passive serial (PS)—An external host supplies the configuration data serially to the
Stratix V FPGA.
■
Joint Test Action Group (JTAG)—Configured using the IEEE Standard 1149.1
interface with a download cable, or using a MAX II device or microprocessor with
flash memory.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Early System and Board Planning
Page 11
You can enable any specific configuration scheme by driving the Stratix V device
MSEL pins to specific values on the board.
12. Select a configuration scheme to plan companion devices and board connections.
f For complete information about the Stratix V device supported configuration
schemes, how to execute the required configuration schemes, and all of the necessary
option pin settings, including the MSEL pin settings, refer to the Configuration, Design
Security, Remote System Upgrades with Stratix V Devices chapter in volume 1 of the
Stratix V Device Handbook.
All configuration schemes use a configuration device, a download cable, or an
external controller (for example, a MAX II device or microprocessor).
Serial Configuration Devices
Altera serial configuration devices (EPCS) and quad-serial configuration devices
(EPCQ) are used in the AS configuration scheme.
f For information about EPCS and EPCQ configuration devices, refer to volume 2 of the
Configuration Handbook.
Serial configuration devices can be programmed using a USB-Blaster™,
EthernetBlaster, or the ByteBlaster™ II download cable with the Quartus II software.
Alternatively, you can use the Altera programming unit (APU), supported third-party
programmers such as BP Microsystems and System General, or a microprocessor with
the SRunner software driver. SRunner is a software driver developed for embedded
serial configuration device programming that designers can customize to fit in
different embedded systems.
13.
If you want to use the AS configuration mode with large device densities, confirm there is a
configuration device available that is large enough for your target FPGA density.
f For more information about the SRunner software, refer to AN 418: SRunner: An
Embedded Solution for Serial Configuration Device Programming and the source code on
the Altera website (www.altera.com).
Serial configuration devices do not directly support the JTAG interface; however, you
can program the device with JTAG download cables using the Serial FlashLoader
(SFL) feature in the Quartus II software. This feature uses the FPGA as a bridge
between the JTAG interface and the configuration device, allowing both devices to
use the same JTAG interface.
1
Programming the EPCS using the SFL solution is slower than using the standard AS
interface because it must configure the FPGA before programming EPCS or EPCQ
configuration devices.
f For more details about the SFL, refer to AN 370: Using the Serial FlashLoader with the
Quartus II Software.
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Stratix V Device Design Guidelines
Page 12
Early System and Board Planning
Download Cables
The Quartus II programmer supports configuration of Stratix V devices directly using
PS or JTAG interfaces with Altera programming download cables. You can download
design changes directly to the device with Altera download cables, making
prototyping easy and enabling you to make multiple design iterations in quick
succession. You can use the same download cable to program configuration devices
on the board and use JTAG debugging tools such as the SignalTap™ II Embedded
Logic Analyzer.
f For more information about how to use Altera’s download cables, refer to the
following documents:
■
ByteBlaster II Download Cable User Guide
■
USB Blaster Download Cable User Guide
■
EthernetBlaster Communications Cable User Guide
Using the Parallel Flash Loader Megafunction with MAX II Devices
If your system already contains common flash interface (CFI) flash memory, you can
utilize it for Stratix V device configuration storage as well. You can program CFI flash
memory devices through the JTAG interface with the parallel flash loader (PFL)
megafunction in MAX II devices. The PFL also provides the logic to control
configuration from the flash memory device to the Stratix V device and supports
compression to reduce the size of your configuration data. Both PS and FPP
configuration modes are supported using the PFL feature.
14. If you want to use a flash device with the parallel flash loader, check the list of supported devices.
f For more information about the PFL, refer to the Parallel Flash Loader Megafunction
User Guide.
Configuration Features
This section describes Stratix V configuration features and how they affect your
design process.
15.
Ensure your configuration scheme and board support the following required features: data
decompression, design security, remote upgrades, single event updates (SEU) mitigation.
f For more information about these features, refer to the Configuration, Design Security,
Remote System Upgrades with Stratix V Devices chapter in volume 1 of the Stratix V
Device Handbook.
Data Compression
When you enable data compression, the Quartus II software generates configuration
files with compressed configuration data. This compressed file reduces the storage
requirements in the configuration device or flash memory, and decreases the time
required to transmit the bitstream to the Stratix V device.
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December 2013 Altera Corporation
Early System and Board Planning
Page 13
Stratix V devices support decompression in the FPP, AS, and PS configuration
schemes. Use the Stratix V decompression feature if you use the PS mode to reduce
configuration time. The Stratix V decompression feature is not available in the JTAG
configuration scheme.
When compression is turned on, the DCLK to DATA ratio changes accordingly based on
the FPP configuration scheme selected (FPP ×8, FPP ×16, or FPP ×32). To ensure a
successful configuration, the configuration controller must send the DCLK that meets
the DCLK to DATA ratio.
f For more information about DCLK to DATA ratio required for your system, refer to the
Configuration, Design Security, Remote System Upgrades with Stratix V Devices chapter in
volume 1 of the Stratix V Device Handbook.
Design Security Using Configuration Bitstream Encryption
The design security feature ensures that Stratix V designs are protected from copying,
reverse engineering, and tampering. Stratix V devices have the ability to decrypt
configuration bitstreams using the AES algorithm, an industry standard encryption
algorithm that is FIPS-197 certified. Stratix V devices have a design security feature
which utilizes a 256-bit security key.
The design security feature is available in the FPP, AS, or PS configuration schemes.
The design security feature is not available in JTAG configuration scheme.
When the compression is turned on, the DCLK to DATA ratio changes accordingly based
on the FPP configuration scheme selected (FPP ×8, FPP ×16, or FPP ×32). To ensure a
successful configuration, the configuration controller must send the DCLK that meets
the DCLK to DATA ratio.
f For more information about DCLK to DATA ratio required for your system, refer to the
Configuration, Design Security, Remote System Upgrades with Stratix V Devices chapter in
volume 1 of the Stratix V Device Handbook.
Remote System Upgrades
Remote system upgrades help deliver feature enhancements and bug fixes without
costly recalls, and reduces time-to-market, extends product life, and helps avoid
system downtime. Stratix V devices feature dedicated remote system upgrade
circuitry. Soft logic (either the Nios II embedded processor or user logic) implemented
in a Stratix V device can download a new configuration image from a remote location,
store it in the configuration memory, and direct the dedicated remote system upgrade
circuitry to initiate a reconfiguration cycle.
Stratix V devices support remote system upgrades only in the single-device AS
configuration scheme with EPCS and EPCQ devices. You can implement remote
system upgrades in conjunction with design security and real-time decompression of
configuration data. To implement the remote system upgrade interface, use the
ALTREMOTE_UPDATE megafunction.
f For more information about the ALTREMOTE_UPDATE megafunction, refer to the
Remote Update Circuitry Megafunction User Guide (ALTREMOTE_UPDATE).
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Early System and Board Planning
SEU Mitigation and CRC Error Checks
Dedicated circuitry is built into Stratix V devices for a cyclic redundancy check (CRC)
error detection feature that optionally checks for SEUs continuously and
automatically. This allows you to confirm that the configuration data stored in a
Stratix V device is correct and alerts the system to a configuration error. To use the
SEU mitigation features, use the appropriate megafunction for CRC error detection.
Use the CRC_ERROR pin to flag errors and design your system to take appropriate
action. If you do not enable the CRC error detection feature, the CRC_ERROR pin is
available as a design I/O.
f For more information about SEUs, refer to the SEU Mitigation in Stratix V Devices
chapter in volume 1 of the Stratix V Device Handbook.
Quartus II Configuration Settings
This section covers several configuration options that you can set in the Quartus II
software before compilation to generate configuration or programming files. Your
board and system design are affected by these settings and pins, so consider them in
the planning stages. Set the options on the General category of the Device and Pin
Options dialog box.
Optional Configuration Pins
You can enable the following optional configuration pins:
■
CLKUSR—The Enable user-supplied start-up clock (CLKUSR) option enables you
to select which clock source is used for initialization, either the internal oscillator
or an external clock provided on the CLKUSR pin. CLKUSR also allow you to drive the
AS configuration clock (DCLK) at 125 MHz maximum. You can enable this feature
in the Configuration page of the Device and Pins Option dialog box.
■
INIT_DONE—To check if the device has completed initialization and is in user
mode, you can monitor the INIT_DONE pin. Enable the INIT_DONE pin with the
Enable INIT_DONE output option. During the reset stage, after the device exits
POR, and during the beginning of configuration, the INIT_DONE pin is tri-stated
and pulled high due to an external pull-up resistor. The INIT_DONE pin is an opendrain output and requires an external pull-up to VCCPGM.
16. Plan the board design to support optional configuration pins CLKUSR and INIT_DONE, as required.
Restart the Configuration After an Error
You can enable the Auto-restart after configuration error option so that when a
configuration error occurs, the device drives nSTATUS low, which resets the device
internally. The device releases its nSTATUS pin after a reset time-out period. This
enables you to re-initiate the configuration cycle. The nSTATUS pin requires an external
10-k pull-up resistor to VCCPGM.
17. Plan board design to use the Auto-restart after configuration error option.
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Early System and Board Planning
Page 15
Planning for On-Chip Debugging
On-chip debugging is an optional step in the design flow, and different debugging
tools work better for different systems and different designers. Evaluate on-chip
debugging options early in your design process to ensure that your system board,
Quartus II project, and design are able to support the appropriate options. Planning
can reduce time spent debugging, and eliminates design changes later to
accommodate your preferred debugging methodologies. Adding debug pins might
not be enough, because of internal signal accessibility and I/O pin accessibility on the
device. First, select your preferred debugging tool(s) as described in “On-Chip
Debugging Tools” and then refer to “Planning Guidelines for Debugging Tools”.
On-Chip Debugging Tools
The Quartus II portfolio of verification tools includes the following in-system
debugging features:
December 2013
■
SignalProbe incremental routing—Quickly routes internal signals to I/O pins
without affecting the routing of the original design. Starting with a fully routed
design, you can select and route signals for debugging to either previously
reserved or currently unused I/O pins.
■
SignalTap II Embedded Logic Analyzer—Probes the state of internal and I/O
signals without the use of external equipment or extra I/O pins, while the design
is running at full speed in an FPGA device. Defining custom trigger-condition
logic provides greater accuracy and improves the ability to isolate problems. It
does not require external probes or changes to the design files to capture the state
of the internal nodes or I/O pins in the design; all captured signal data is stored in
the device memory until you are ready to read and analyze the data. The
SignalTap II Embedded Logic Analyzer works best for synchronous interfaces. For
debugging asynchronous interfaces, consider using SignalProbe or an external
logic analyzer to view the signals more accurately.
■
Logic Analyzer Interface—Enables you to connect and transmit internal FPGA
signals to an external logic analyzer for analysis, allowing you to take advantage
of advanced features in your external logic analyzer or mixed signal oscilloscope.
You can use this feature to connect a large set of internal device signals to a small
number of output pins for debugging purposes and it can multiplex signals with
design I/O pins if required.
■
In-System Memory Content Editor—Provides read and write access to in-system
FPGA memories and constants through the JTAG interface, so you can test
changes to memory content and constant values in the FPGA while the device is
functioning in the system.
■
In-System Sources and Probes—Sets up customized register chains to drive or
sample the instrumented nodes in your logic design, providing an easy way to
input simple virtual stimuli and capture the current value of instrumented nodes.
■
Virtual JTAG megafunction—Enables you to build your own system-level
debugging infrastructure, including both processor-based debugging solutions
and debugging tools in the software for system-level debugging. You can
instantiate the SLD_VIRTUAL_JTAG megafunction directly in your HDL code to
provide one or more transparent communication channels to access parts of your
FPGA design using the JTAG interface of the device.
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Pin Connection Considerations for Board Design
f For more information about these debugging tools, refer to the Virtual JTAG
(sld_virtual_jtag) Megafunction User Guide and Section IV. In-System Design Debugging in
volume 3 of the Quartus II Handbook. The section overview provides more information
about choosing a debugging solution.
18.
Take advantage of on-chip debugging features to analyze internal signals and perform advanced
debugging techniques.
Planning Guidelines for Debugging Tools
If you intend to use any of the on-chip debugging tools, plan for the tool(s) when
developing the system board, Quartus II project, and design, as described in the
following checklist:
19.
Select on-chip debugging scheme(s) early to plan memory and logic requirements, I/O pin
connections, and board connections.
If you want to use SignalProbe incremental routing, the SignalTap II Embedded Logic Analyzer, Logic
20. Analyzer Interface, In-System Memory Content Editor, In-System Sources and Probes, or Virtual JTAG
megafunction, plan your system and board with JTAG connections that are available for debugging.
21.
Plan for the small amount of additional logic resources used to implement the JTAG hub logic for
JTAG debugging features.
22.
For debugging with the SignalTap II Embedded Logic Analyzer, reserve device memory resources to
capture data during system operation.
23.
Reserve I/O pins for debugging with SignalProbe or the Logic Analyzer Interface so you do not have to
change the design or board to accommodate debugging signals later.
24.
Ensure the board supports a debugging mode where debugging signals do not affect system
operation.
25.
Incorporate a pin header or mictor connector as required for an external logic analyzer or mixed signal
oscilloscope.
26.
To use debug tools incrementally and reduce compilation time, ensure incremental compilation is on
so you do not have to recompile the design to modify the debug tool.
27.
To use the Virtual JTAG megafunction for custom debugging applications, instantiate it in the HDL
code as part of the design process.
28. To use the In-System Sources and Probes feature, instantiate the megafunction in the HDL code.
To use the In-System Memory Content Editor for RAM or ROM blocks or the LPM_CONSTANT
29. megafunction, turn on the Allow In-System Memory Content Editor to capture and update content
independently of the system clock option for the memory block in the MegaWizard™ Plug-In Manager.
Pin Connection Considerations for Board Design
When designing the interfaces to the Stratix V device, various factors can affect the
PCB design. This section includes important guidelines for the following topics:
■
“Device Power-Up”
■
“Power Pin Connections and Power Supplies” on page 18
■
“Configuration Pin Connections” on page 20
■
“Board-Related Quartus II Settings” on page 22
■
“Signal Integrity Considerations” on page 23
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Pin Connection Considerations for Board Design
■
Page 17
“Board-Level Simulation and Advanced I/O Timing Analysis” on page 25
“I/O and Clock Planning” on page 25 discusses the I/O signal connections for the
FPGA, which also affect the board design.
Device Power-Up
Stratix V devices offer hot socketing, which is also known as hot plug-in or hot swap,
and power sequencing support without the use of external devices. You can insert or
remove a Stratix V device or a board in a system during system operation without
causing undesirable effects to the running system bus or the board inserted into the
system. The hot socketing feature helps you use Stratix V devices on PCBs that
contain a mixture of I/O standards powered by different voltages.
f For more information about the hot socketing capabilities of I/O pins, and for
power-on reset circuitry details that must be considered for all Stratix V designs, refer
to the Hot Socketing and Power-On Reset in Stratix V Devices chapter.
30.
Design board for power-up: Stratix V output buffers are tri-stated until the device is configured and
configuration pins drive out.
31. Design voltage power supply ramps to be monotonic.
1
The minimum current requirement for the power-on-reset (POR) supplies must be
available during device power up.
Stratix V devices do not exit POR if VCCIO and VCCPD are powered by the same
regulator and not enough current is available during power up. If the VCCIO, VCCPD,
and VCCPGM are powered by the same regulator and not enough current is available
during power up, Stratix V devices do not enter POR. For recommendation about
combining supplies, refer to the Stratix V Pin Connection Guidelines, and for minimum
current requirement, use the PowerPlay Early Power Estimator spreadsheet or refer to
the Quartus II PowerPlay Power Analyzer report file.
In Stratix V devices, a pin-selectable option (PORSEL) allows you to select between a
typical POR time setting of 4 ms or 100 ms. In both cases, you can extend the POR
time by using an external component to assert the nSTATUS pin low. Extend POR time
if the board cannot meet the maximum power ramp time specifications to ensure the
device configures properly and enters user mode.
32.
Set POR time to ensure power supplies are stable.
Stratix V devices have power sequencing requirements. You should consider the
power-up timing for each rail in order to meet the power sequencing requirements as
described in the Power Management in Stratix V Devices chapter in the Stratix V Device
Handbook.
33.
December 2013
Design power sequencing and voltage regulators for best device reliability. Connect the GND between
boards before connecting the power supplies.
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Pin Connection Considerations for Board Design
Altera uses GND as a reference for hot-socketing operations and I/O buffer designs.
Connecting the GND between boards before connecting the power supplies prevents
the GND on your board from being pulled up inadvertently by a path to power
through other components on your board. A pulled up GND could otherwise cause
an out-of-specification I/O voltage or current condition with the Altera device.
f For more information, refer to the Power Management in Stratix V Devices chapter in the
Stratix V Device Handbook.
Power Pin Connections and Power Supplies
Stratix V devices require various voltage supplies depending on your design
requirements. To verify the core voltage, PLL digital power supply, programmable
technology voltage, and other voltage supply levels, refer to the Stratix V Device
Family Pin Connection Guidelines.
f For a list of the supply voltages required for Stratix V devices and their recommended
operation conditions, refer to the DC and Switching Characteristics for Stratix V Devices
chapter in volume 3 of the Stratix V Device Handbook.
Stratix V devices support a wide range of industry I/O standards, such as VCCIO
voltage levels of 3.0, 2.5, 1.8, 1.5, 1.35, 1.25, and 1.2 V.
1
The device output pins do not meet the I/O standard specifications if the VCCIO level
is out of the recommended operating range for the I/O standard. The VCCPD pin must
be connected to 3.0 V for a 3.0-V VCCIO and 2.5 V for 2.5 or lower I/O voltages.
f For a complete list of the supported I/O standards and VCCIO voltages, refer to the I/O
Features in Stratix V Devices chapter.
Voltage reference (VREF) pins serve as voltage references for certain I/O standards.
The VREF pin is used mainly for a voltage bias and does not source or sink much
current. The voltage can be created with a regulator or a resistor divider network. For
more information about VCCIO voltages and VREF pins for different I/O banks, refer
to “Selectable I/O Standards and Flexible I/O Banks” on page 28.
f For details about I/O power pin connections, refer to the Stratix V Device Family Pin
Connection Guidelines.
34. Connect all power pins correctly as specified in the Stratix V Device Family Pin Connection Guidelines.
35. Connect VCCIO pins and VREF pins to support each bank’s I/O standards.
36. Connect the VCCPD pin to 3.0 V for a 3.0-V VCCIO, and 2.5 V for lower I/O voltages.
37.
Explore unique requirements for FPGA power pins or other power pins on your board, and determine
which devices on your board can share a power rail.
38.
Follow the suggested power supply sharing and isolation guidance, and the specific guidelines for
each pin in the Stratix V Device Family Pin Connection Guidelines.
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December 2013 Altera Corporation
Pin Connection Considerations for Board Design
Page 19
Decoupling Capacitors
Board decoupling is important for improving overall power supply integrity while
ensuring the rated device performance.
Stratix V devices include embedded on-package and on-die decoupling capacitors to
provide high-frequency decoupling. These low-inductance capacitors suppress power
noise for excellent power integrity performance, and reduce the number of external
PCB decoupling capacitors, saving board space, reducing cost, and greatly
simplifying PCB design.
Altera has created an easy-to-use power distribution network (PDN) design tool that
optimizes the board-level PDN graphically. The purpose of the board-level PDN is to
distribute power and return currents from the voltage regulating module (VRM) to the
FPGA power supplie. By using the PDN tool, designers can quickly arrive at an
optimized PDN decoupling solution for their specific design.
For each power supply, PDN designers must choose a network of bulk and
decoupling capacitors. While SPICE simulation could be used to simulate the circuit,
the PDN design tool provides a fast, accurate, and interactive way to determine the
right number of decoupling capacitors for optimal cost and performance trade-offs.
39. Use the PDN tool to plan your power distribution netlist and decoupling capacitors.
PLL Board Design Guidelines
For more information about designing your clock and PLL scheme, refer to “Clock
and PLL Selection” on page 33 and “PLL Feature Guidelines” on page 35. Consider
the following checklist items when you design a power system for PLL usage and to
minimize jitter, because PLLs contain analog components embedded in a digital
device.
40.
Connect all PLL power pins to reduce noise even if the design does not use all the PLLs. For pin
voltage requirements, refer to the Stratix V Device Family Pin Connection Guidelines.
41.
Power supply nets should be provided by an isolated power plane, a power plane cut out, or thick
trace of at least 20 mils.
f For more board design guidelines related to PLL power supplies, refer to the “General
Board Design Considerations/Guidelines” section of the Board Design Resource
Center.
Transceiver Board Design Guidelines
For information about transceiver board design guidelines, refer to “Appendix:
Stratix V Transceiver Design Guidelines” on page 59.
f For guidelines specific to transceiver design, refer to the Stratix V Device Handbook,
Volume 2.
f For board design guidelines related to high-speed transceivers, refer to the “Gigahertz
Channel Design Considerations” section of the Board Design Resource Center.
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Pin Connection Considerations for Board Design
Configuration Pin Connections
Depending on your configuration scheme, different pull-up/pull-down resistor or
signal integrity requirements might apply. Some configuration pins also have specific
requirements if unused. It is very important to connect the configuration pins
correctly. This section contains guidelines to address common issues.
42.
Check that all configuration pin connections and pull-up/pull-down resistors are set correctly for your
configuration scheme(s).
f For specifics about each configuration pin, refer to the Stratix V Device Family Pin
Connection Guidelines.
f For a list of the dedicated and dual-purpose configuration pins, and a description of
the function, refer to the Configuration, Design Security, Remote System Upgrades with
Stratix V Devices chapter in volume 1 of the Stratix V Device Handbook.
DCLK and TCK Signal Integrity
The TCK and/or DCLK traces should produce clean signals with no overshoot,
undershoot, or ringing. When designing the board, lay out the TCK and DCLK traces
with the same techniques used to lay out a clock line. Any overshoot, undershoot,
ringing, or other noise on the TCK signal can affect JTAG configuration. A noisy DCLK
signal can affect configuration and cause a CRC error. For a chain of devices, noise on
any of the TCK or DCLK pins in the chain could cause JTAG programming or
configuration to fail for the entire chain.
43. Design configuration DCLK and TCK pins to be noise-free.
f For more information about connecting devices in a chain, refer to the Configuration,
Design Security, Remote System Upgrades with Stratix V Devices chapter in volume 1 of
the Stratix V Device Handbook.
JTAG Pins
Because JTAG configuration takes precedence over all other configuration methods,
the JTAG pins should not be left floating or toggling during configuration if you do
not use the JTAG interface. If you use the JTAG interface, follow the guidelines in this
section.
44. Connect JTAG pins to a stable voltage level if not in use.
JTAG Pin Connections
A device operating in JTAG mode uses four required pins—TDI, TDO, TMS, and TCK—
and one optional pin, TRST. The TCK pin has an internal weak pull-down resistor, while
the TDI, TMS, and TRST pins have weak internal pull-up resistors. The JTAG output pin
TDO and all JTAG input pins are powered by the 2.5 and 3.0 VCCPD. All JTAG pins are
tri-stated during JTAG reconfiguration.
45. Connect JTAG pins correctly to the download cable header. Ensure the pin order is not reversed.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Pin Connection Considerations for Board Design
Page 21
If you have more than one device in the chain, connect the TDO pin of a device to the
TDI pin of the next device in the chain.
Noise on the JTAG pins during configuration, user mode, or power-up can cause the
device to go into an undefined state or mode.
46.
To disable the JTAG state machine during power-up, pull the TCK pin low through a 1-k resistor to
ensure that an unexpected rising edge does not occur on TCK.
47. Pull TMS and TDI high through a 1-k to 10-k resistor.
48. Connect TRST directly to VCCPD (Connecting the pin low disables the JTAG circuitry).
Download Cable Operating Voltage
The operating voltage supplied to the Altera download cable by the target board
through the 10-pin header determines the operating voltage level of the download
cable.
In a JTAG chain containing devices with different VCCIO levels, the devices with a
higher VCCIO level should drive the devices with the same or lower VCCIO level. A
one-level shifter is required at the end of the chain with this device arrangement. If
this arrangement is not possible, you have to add more level shifters into the chain.
49.
Because the download cable interfaces with the JTAG pins of your device, ensure the download cable
and JTAG pin voltages are compatible.
f For recommendations about connecting a JTAG chain with multiple voltages across
the devices in the chain, refer to the JTAG Boundary-Scan Testing in Stratix V Devices
chapter in volume 1 of the Stratix V Device Handbook.
JTAG Signal Buffering
You might have to add buffers to a JTAG chain, depending on the JTAG signal
integrity, especially the TCK signal, because it is the JTAG clock and the fastest
switching JTAG signal. Altera recommends buffering the signals at the connector
because cables and board connectors tend to make bad transmission lines and
introduce noise to the signals. After this initial buffer at the connector, add buffers as
the chain gets longer or whenever the signals cross a board connector.
If a cable drives three or more devices, buffer the JTAG signal at the cable connector to
prevent signal deterioration. Of course, this also depends on the board layout, loads,
connectors, jumpers, and switches on the board. Anything added to the board that
affects the inductance or capacitance of the JTAG signals increases the likelihood that
a buffer should be added to the chain.
Each buffer should drive no more than eight loads for the TCK and TMS signals, which
drive in parallel. If jumpers or switches are added to the path, decrease the number of
loads.
50.
Buffer JTAG signals per the recommendations, especially for connectors or if the cable drives more
than three devices.
51. If your device is in a configuration chain, ensure all devices in the chain are connected properly.
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Pin Connection Considerations for Board Design
MSEL Configuration Mode Pins
Select the configuration scheme by driving the Stratix V device MSEL pins high or
low. JTAG configuration is always available, regardless of the MSEL pin selection. The
MSEL pins are powered by the VCCPGM power supply of the residing bank. The
MSEL[4..0] pins have 5 k- internal pull-down resistors that are always active.
During POR and reconfiguration, the MSEL pins must be at LVTTL VIL and VIH levels
to be considered a logic low and logic high, respectively. To avoid problems with
detecting an incorrect configuration scheme, hardwire the MSEL pins to VCCPGM or
GND without pull-up or pull-down resistors. Do not drive the MSEL pins with a
microprocessor or another device.
Connect the MSEL pins to a select configuration scheme; do not leave them floating. For flexibility to
52. change between configuration modes during testing or debugging, set up the board to connect each
pin to either VCCPGM or GND without pull-up or pull-down resistors.
Other Configuration Pins
Ensure all dedicated and dual-purpose configuration pins are connected correctly.
53. Connect nIO_PULLUP directly to GND.
54.
Hold the nCE (chip enable) pin low during configuration, initialization, and user mode.
In single device configuration or JTAG programming, tie nCE low. In multi-device
configuration, tie nCE low on the first device and connect its nCEO pin to the nCE pin on
the next device in the chain.
Board-Related Quartus II Settings
The Quartus II software provides options for the FPGA I/O pins that you should
consider during board design. Ensure that these options are set correctly when the
Quartus II project is created, and plan for the functionality during board design.
Device-Wide Output Enable Pin
Stratix V devices support an optional chip-wide output enable that allows you to
override all tri-states on the device I/Os. When this DEV_OE pin is driven low, all I/O
pins are tri-stated; when this pin is driven high, all pins behave as programmed. To
use this chip-wide output enable, turn on Enable device-wide output enable
(DEV_OE) in the Quartus II software before compiling your design in the General
category of the Device and Pin Options dialog box. Ensure this pin is driven to a
valid logic level on your board if you enable this pin in the Quartus II software. Do
not leave this pin floating.
55.
Turn on the device-wide output enable option, if required.
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Pin Connection Considerations for Board Design
Page 23
Unused Pins
You can specify the state of unused pins in the Quartus II software to allow flexibility
in the board design by choosing one of the five allowable states for Reserve all
unused pins on the Unused Pins category in the Device and Pin Options dialog box:
■
As inputs tri-stated
■
As output driving ground
■
As outputs driving an unspecified signal
■
As input tri-stated with bus-hold circuitry
■
As input tri-stated with weak pull-up
56. Specify the reserved state for unused I/O pins.
The common setting is to set unused pins As inputs tri-stated with weak pull-up. To
improve signal integrity, set the unused pins to As output driving ground. Doing this
reduces inductance by creating a shorter return path and reduces noise on the
neighboring I/Os. This approach should not be used if this results in many via paths
causing congestion for signals under the device.
To reduce power dissipation, set clock pins and other unused I/O pins As inputs
tri-stated, and tie them to ground.
57.
Carefully check the pin connections in the Quartus II software-generated .pin. Do not connect
RESERVED pins.
Signal Integrity Considerations
This section contains references to detailed board design guidelines, as well as a few
guidelines related to VREF pins, SSN, and I/O termination.
High-Speed Board Design
If your design has high-speed signals, especially with Stratix V GX device high-speed
transceivers, the board design has a major impact on the signal integrity in the system.
f For detailed information about signal integrity and board design, refer to the Board
Design Resource Center. For example, Altera provides the following application notes
that offer information about high-speed board stack-up and signal routing layers:
December 2013
■
AN 528: PCB Dielectric Material Selection and Fiber Weave Effect on High-Speed
Channel Routing
■
AN 529: Via Optimization Techniques for High-Speed Channel Designs
■
AN 530: Optimizing Impedance Discontinuity Caused by Surface Mount Pads for
High-Speed Channel Designs
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Pin Connection Considerations for Board Design
Voltage Reference Pins
Voltage deviation on a VREF pin can affect the threshold sensitivity for inputs.
58. Design VREF pins to be noise-free.
For more information about VREF pins and I/O standards, refer to “I/O Features and
Pin Connections” on page 27.
Simultaneous Switching Noise
SSN is a concern when too many pins (in close proximity) change voltage levels at the
same time. Noise generated by SSN can reduce the noise margin and cause incorrect
switching. Although SSN is dominant on the device package, refer to the PCB
guidelines in Altera’s Board Design Guidelines Solution Center for board layout
recommendations that can help with noise reduction. For example, consider the
following items:
59. Break out large bus signals on board layers close to the device to reduce cross talk.
60.
Route traces orthogonally if two signal layers are next to each other, if possible. Use a separation of 2
to 3 times the trace width.
I/O Termination
Voltage-referenced I/O standards require both an VREF and a termination voltage
(VTT). The reference voltage of the receiving device tracks the termination voltage of
the transmitting device. Each voltage-referenced I/O standard requires a unique
termination setup. For example, a proper resistive signal termination scheme is
critical in SSTL-2 standards to produce a reliable DDR memory system with superior
noise margin.
Although single-ended, non-voltage-referenced I/O standards do not require
termination, impedance matching is necessary to reduce reflections and improve
signal integrity.
Stratix V on-chip series and parallel termination provides the convenience of no
external components. Alternatively, you can use external pull-up resistors to
terminate the voltage-referenced I/O standards such as SSTL and HSTL.
Differential I/O standards typically require a termination resistor between the two
signals at the receiver. The termination resistor must match the differential load
impedance of the signal line. Stratix V devices provide an optional differential on-chip
resistor when using LVDS.
1
Certain dedicated clock input pairs do not support differential termination.
f For a complete list of on-chip termination (OCT) support for each I/O standard, refer
to the I/O Features in Stratix V Devices chapter.
61.
Check I/O termination and impedance matching for chosen I/O standards, especially for
voltage-referenced standards.
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I/O and Clock Planning
Page 25
For more information about OCT features and limitations, refer to “I/O Features and
Pin Connections” on page 27.
Board-Level Simulation and Advanced I/O Timing Analysis
To ensure that the I/O signaling meets receiver threshold levels on your board setup,
perform full board routing simulation with third-party board-level simulation tools
using an IBIS model.
When this feature is available in the Quartus II software, select IBIS under
Board-level signal integrity analysis on the Board-Level page in EDA Tool Settings
of the Settings dialog box.
62. Perform board-level simulation using IBIS models (when available).
f For more information about this simulation flow, refer to the Signal Integrity with
Third-Party Tools chapter in volume 2 of the Quartus II Handbook.
When you include an FPGA device with high-speed interfaces in a board design,
knowing the signal integrity and board routing propagation delay is vital for proper
system operation. You should analyze board level timing as part of the I/O and board
planning, especially for high-speed designs.
63. Configure board trace models for Quartus II advanced I/O timing analysis.
You can configure board trace models of selected I/O standards and generate
“board-aware” signal integrity reports with the Quartus II software. When Enable
Advanced I/O Timing is turned on (TimeQuest Timing Analyzer page in the
Settings dialog box), the TimeQuest Timing Analyzer uses simulation results for the
I/O buffer, package, and the board trace model to generate more accurate I/O delays
and extra reports to give insight into signal behavior at the system level. You can use
these advanced timing reports as a guide to make changes to the I/O assignments and
board design to improve timing and signal integrity.
I/O and Clock Planning
Planning and allocating I/O and clock resources is an important task with the high
pin counts and advanced clock management features in Stratix V devices. Various
considerations are important to effectively plan the available I/O resources to
maximize utilization and prevent issues related to signal integrity. Good clock
management systems are also crucial to the performance of an FPGA design.
The I/O and clock connections of your FPGA affect the rest of your system and board
design, so it is important to plan these connections early in your design cycle.
This section details the following topics:
December 2013
■
“Making FPGA Pin Assignments” on page 26
■
“Early Pin Planning and I/O Assignment Analysis” on page 26
■
“I/O Features and Pin Connections” on page 27
■
“Clock and PLL Selection” on page 33
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I/O and Clock Planning
■
“PLL Feature Guidelines” on page 35
■
“Clock Control Block” on page 36
Making FPGA Pin Assignments
With the Quartus II Pin Planner GUI, you can identify I/O banks, VREF groups, and
differential pin pairings to help you through the I/O planning process. Right-click in
the Pin Planner spreadsheet interface and click the Pin Finder to search for specific
pins. If migration devices are selected, as described in “Vertical Device Migration” on
page 6, the Pin Migration view highlights pins that change function in the migration
device when compared to the currently selected device.
64. Use the Quartus II Pin Planner to make pin assignments.
You have the option of importing a Microsoft Excel spreadsheet into the Quartus II
software to start the I/O planning process if you normally use a spreadsheet in your
design flow. You can also export a spreadsheet compatible (.csv) file containing your
I/O assignments when all pins are assigned.
When you compile your design in the Quartus II software, I/O Assignment Analysis
in the Fitter validates that the assignments meet all the device requirements and
generates messages if there are any problems.
65.
Use Quartus II Fitter messages and reports for sign-off of pin assignments.
Quartus II designers can then pass the pin location information to PCB designers. Pin
assignments between the Quartus II software and your schematic and board layout
tools must match to ensure the design works correctly on the board where it is placed,
especially if changes to the pin-out must be made. The Pin Planner
is integrated with certain PCB design EDA tools and can read pin location changes
from these tools to check the suggested changes. When you compile your design, the
Quartus II software generates the .pin. You can use this file to verify that each pin is
correctly connected in the board schematics.
66. Verify that the Quartus II pin assignments match those in the schematic and board layout tools.
f For details about using the Pin Planner to make I/O assignments, refer to the I/O
Management chapter in volume 2 of the Quartus II Handbook. For more information
about passing I/O information between the Quartus II software and third-party EDA
tools, refer to the Mentor Graphics PCB Design Tools Support and Cadence PCB Design
Tools Support chapters in volume 2 of the Quartus II Handbook.
Early Pin Planning and I/O Assignment Analysis
In many design environments, FPGA designers want to plan top-level FPGA I/O pins
early so that board designers can start developing the PCB design and layout. The
FPGA device’s I/O capabilities and board layout guidelines influence pin locations
and other types of assignments. In cases where the board design team specifies an
FPGA pin-out, it is crucial that you verify pin locations in the FPGA place-and-route
software as soon as possible to avoid board design changes.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
I/O and Clock Planning
Page 27
You can use the Quartus II Pin Planner for I/O pin assignment planning, assignment,
and validation, as described in “Making FPGA Pin Assignments” on page 26. The
Quartus II Start I/O Assignment Analysis command checks that the pin locations and
assignments are supported in the target FPGA architecture. Checks include reference
voltage pin usage, pin location assignments, and mixing of I/O standards. You can
use I/O Assignment Analysis to validate I/O-related assignments that you make or
modify throughout the design process.
Starting FPGA pin planning early improves the confidence in early board layouts,
reduces the chance of error, and improves the design’s overall time to market. You can
create a preliminary pin-out for an Altera FPGA using the Quartus II Pin Planner
before the source code is designed.
67.
Use the Create Top-Level Design File command with I/O Assignment Analysis to check the I/O
assignments before the design is complete.
Early in the design process, the system architect typically has information about the
standard I/O interfaces (such as memory and bus interfaces), IP cores to be used in
the design, and any other I/O-related assignments defined by system requirements.
The Pin Planner Create/Import Megafunction feature interfaces with the
MegaWizard Plug-In Manager, and enables you to create or import custom
megafunctions and IP cores that use I/O interfaces. Enter PLL and LVDS blocks,
including options such as dynamic phase alignment (DPA), because options affect the
pin placement rules. When you have entered as much I/O-related information as
possible, generate a top-level design netlist file using the Create Top-Level Design
File command in the Pin Planner. You can use the I/O analysis results to change pin
assignments or IP parameters and repeat the checking process until the I/O interface
meets your design requirements and passes the pin checks in the Quartus II software.
When planning is complete, the preliminary pin location information can be passed to
PCB designers as described in the previous section. When the design is complete, use
the reports and messages generated by the Quartus II Fitter for the final sign-off of the
pin assignments.
f For more information about I/O assignment and analysis, refer to the I/O Management
chapter in volume 2 of the Quartus II Handbook.
I/O Features and Pin Connections
Stratix V I/O pins are designed for ease of use and rapid system integration, while
simultaneously providing high bandwidth. Independent modular I/O banks with a
common bank structure for vertical migration lend efficiency and flexibility to the
high speed I/O. This section provides guidelines related to I/O features and pin
connections. It describes support for different I/O signal types and I/O standards in
device I/O banks, as well as other I/O features available for your design. It also
provides information about memory interfaces, pad placement guidelines, and
special pin connections.
f For a list of I/O pin locations and connection guidelines, refer to the Stratix V Device
Family Pin Connection Guidelines.
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Stratix V Device Design Guidelines
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I/O and Clock Planning
I/O Signaling Type
Stratix V devices support a wide range of industry I/O standards, including
single-ended, voltage-referenced single-ended, and differential I/O standards. This
section provides general guidelines for selecting a signaling type.
Single-ended I/O signaling provides a simple rail-to-rail interface. Its speed is limited
by the large voltage swing and noise. Single-ended I/Os do not require termination,
unless reflection in the system causes undesirable effects.
Voltage-referenced signaling reduces the effects of simultaneous switching outputs
(SSO) from pins changing voltage levels at the same time (for example, external
memory interface data and address buses). Voltage-referenced signaling also provides
an improved logic transition rate with a reduced voltage swing, and minimizes noise
caused by reflection with a termination requirement. However, additional termination
components are required for the reference voltage source (VTT).
Differential signaling eliminates the interface performance barrier of single-ended
and voltage-referenced signaling, with superior speed using an additional inverted
closely-coupled data pair. Differential signaling also avoids the requirement for a
clean reference voltage. This is possible because of a lower swing voltage and noise
immunity with a common mode noise rejection capability. Considerations for this
implementation include the requirements for a dedicated PLL to generate a sampling
clock, and matched trace lengths to eliminate the phase difference between an
inverted and non-inverted pair.
Stratix V I/O pins are organized in pairs to support differential standards. Each I/O
pin pair can support differential input or output operations, with the exception of
certain clock pins that support differential input operations only. In your design
source code, define just one pin to represent a differential pair, and make a pin
assignment for this positive end of the pair. When you specify a differential I/O
standard, the Quartus II software automatically places the corresponding negative
pin.
68. Plan the I/O signaling type based on the system requirements.
69. Allow the software to assign locations for the negative pin in differential pin pairs.
Selectable I/O Standards and Flexible I/O Banks
Stratix V I/O pins are arranged in groups called modular I/O banks. Depending on
the device density, the number of I/O banks ranges from 16 to 26 banks, with up to
eight I/O banks per side, depending on the device density.
70. Select a suitable signaling type and I/O standard for each I/O pin.
71. Ensure that the appropriate I/O standard support is supported in the targeted I/O bank.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
I/O and Clock Planning
Page 29
Certain I/O banks on the top and bottom or left and right of the device support
different I/O standards and voltage levels. You can assign I/O standards and make
other I/O-related settings in the Pin Planner. Be sure to use the correct dedicated pin
inputs for signals such as clocks and global control signals, as described in “Clock and
PLL Selection” on page 33.
72. Place I/O pins that share voltage levels in the same I/O bank.
73. Verify that all output signals in each I/O bank are intended to drive out at the bank’s VCCIO voltage level.
74.
Verify that all voltage-referenced signals in each I/O bank are intended to use the bank’s VREF voltage
level.
The board must supply each bank with one VCCIO voltage level for every VCCIO pin in
a bank. Each I/O bank is powered by the VCCIO pins of that particular bank, and is
independent of the VCCIO of other I/O banks. A single I/O bank supports output
signals that are driving at the same voltage as the VCCIO. An I/O bank can
simultaneously support any number of input signals with different I/O standards.
To accommodate voltage-referenced I/O standards, each I/O bank supports multiple
VREF pins feeding a common VREF bus. Set the VREF pins to the correct voltage for
the I/O standards in the bank. Each I/O bank can only have a single VCCIO voltage
level and a single VREF voltage level at a given time. If the VREF pins are not used as
voltage references, they cannot be used as generic I/O pins and should be tied to
VCCIO of that same bank or GND.
An I/O bank including single-ended or differential standards can support
voltage-referenced standards as long as all voltage-referenced standards use the same
VREF setting. For performance reasons, voltage referenced input standards use their
own VCCPD level as the power source, so you can place voltage-referenced input
signals in a bank with a VCCIO of 2.5 V or below. Voltage-referenced bi-directional and
output signals must drive out at the I/O bank’s VCCIO voltage level.
Different I/O banks include different support for LVDS signaling, and the Stratix V
transceiver banks include additional support.
75. Check the I/O bank support for LVDS and transceiver features.
f For information about the number of channels available for the LVDS I/O standard,
refer to the High-Speed Differential I/O Interface and DPA in Stratix V Devices chapter in
volume 1 of the Stratix V Device Handbook. For more information about
transceiver-bank-related features, refer to the Transceiver Architecture in Stratix V
Devices chapter in volume 2 of the Stratix V Device Handbook.
f For more information about I/Os, refer to the I/O Features in Stratix V Devices chapter
in volume 1 of the Stratix V Device Handbook.
f For the electrical characteristics of each I/O standard, refer to the DC and Switching
Characteristics for Stratix V Devices chapter in volume 3 of the Stratix V Device
Handbook.
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Stratix V Device Design Guidelines
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I/O and Clock Planning
Memory Interfaces
Stratix V devices provide an efficient architecture to quickly and easily fit wide
external memory interfaces with their small modular I/O banks. Stratix V devices
support DDR3, DDR2, DDR SDRAM, QDRII+, QDRII SRAM, and RLDRAM II. The
Stratix V FPGA can support DDR external memory on any I/O banks on all sides of
the device that do not support transceivers.
76.
Use the UniPHY megafunction (or IP core) for each memory interface, and follow connection
guidelines/restrictions in the appropriate documentation.
The self-calibrating UniPHY megafunction is optimized to take advantage of the
Stratix V I/O structure. The UniPHY megafunction allows you to set external memory
interface features and helps set up the physical interface (PHY) best suited for your
system. When you use the Altera memory controller MegaCore functions, the
UniPHY megafunction is instantiated automatically.
If you design multiple memory interfaces into the device using Altera IP, generate a
unique interface for each instance to ensure good results instead of designing it once
and instantiating it multiple times.
77. Use dedicated DQ/DQS pins and DQ groups for memory interfaces.
The data strobe DQS and data DQ pin locations are fixed in Stratix V devices. Before
you design your device pin-out, refer to the memory interface guidelines for details
and important restrictions related to the connections for these and other memoryrelated signals.
f Refer to the following documents for more information about a specific external
memory interface topic:
■
For connecting a Stratix V device with external memory devices and pin planning,
refer to Volume 2: Device, Pin, and Board Layout Guidelines of the External Memory
Interface Handbook.
■
For memory speeds and maximum clock rates, refer to the External Memory
Interface Spec Estimator.
■
For information about the UniPHY megafunction, refer to the following user
guides:
■
■
DDR2 and DDR3 SDRAM Controller with UniPHY User Guide
■
QDR II and QDR II+ SRAM Controller with UniPHY User Guide
■
RLDRAM II Controller with UniPHY IP User Guide
For additional resources, refer to the External Memory Solutions Center.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
I/O and Clock Planning
Page 31
Dual-Purpose and Special Pin Connections
Stratix V devices allow I/O flexibility with dual-purpose configuration pins. You can
use dual-purpose configuration pins as general I/Os after device configuration is
complete. Select the desired setting for each of the dual-purpose pins on the
Dual-Purpose Pins category of the Device and Pin Options dialog box. Depending
on the configuration scheme, these pins can be reserved as regular I/O pins, as inputs
that are tri-stated, as outputs that drive ground, or as outputs that drive an
unspecified signal.
You can also use dedicated clock inputs, which drive the GCLK networks, as generalpurpose input pins if they are not used as clock pins. When you use the clock inputs
as general inputs, I/O registers use ALM-based registers because the clock input pins
do not include dedicated I/O registers.
The device-wide reset and clear pins are available as design I/Os if they are not
enabled. For more information, refer to “Device-Wide Output Enable Pin” on page 22
and “Register Power-Up Levels and Control Signals” on page 39.
78. Make dual-purpose pin settings and check for any restrictions when using these pins as regular I/O.
Stratix V I/O Features
The Stratix V bi-directional I/O element (IOE) features support rapid system
integration while simultaneously providing the high bandwidth required to
maximize internal logic capabilities and system-level performance. Advanced
features for device interfaces assist in high-speed data transfer into and out of the
device and reduce the complexity and cost of the PCB. Table 2 lists Stratix V I/O
features, provides usage information and design considerations, and provides
references for more information about the features.
Table 2. Stratix V I/O Features
Feature
MultiVolt I/O
Interface
3.3-V I/O Interface
December 2013
Usage
Guidelines and More Information
Allows all packages to interface with systems of
different supply voltages. VCCIO pins can be
connected to a 1.2-, 1.25-, 1.35-, 1.5-, 1.8-, 2.5-,
or 3.0-V power supply, depending on the output
requirements. The output levels are compatible
with systems of the same voltage as the power
supply. VCCPD power pins must be connected to a
2.5- or 3.0-V power supply.
Refer to the previous sections and the I/O
Features in Stratix V Devices chapter in volume 1
of the Stratix V Device Handbook for a summary
of MultiVolt I/O support and a list of the
supported I/O standards and the typical values for
input and output VCCIO, VCCPD, VREF, and board
termination voltage (VTT). Altera recommends that
you use an external clamp diode on the all I/O
pins when the input signal is 3.0 V or 3.3 V.
Stratix V I/O buffers support 3.3-V I/O standards
as transmitters or receivers in your system. The
output high voltage (VOH), output low voltage
(VOL), input high voltage (VIH), and input low
voltage (VIL) levels meet the 3.3-V I/O standards
specifications when the Stratix V VCCIO voltage is
powered by 3.0 V.
To ensure device reliability and proper operation
when interfacing with a 3.3-V I/O system, it is
important to make sure that the absolute
maximum ratings of the Stratix V device are not
violated. Altera recommends performing an IBIS
or SPICE simulation to determine that the
overshoot and undershoot voltages are within the
specifications. For more information, refer to the
I/O Features in Stratix V Devices chapter in
volume 1 of the Stratix V Device Handbook.
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I/O and Clock Planning
Table 2. Stratix V I/O Features
Feature
Usage
Guidelines and More Information
Programmable
Output Current
Strength
Programmable current-strength control is
available for certain I/O standards. You can
mitigate the effects of high signal attenuation due
to a long transmission line or a legacy backplane.
A higher current strength increases I/O
performance, but also increases noise on the
interface, so you can use current strength control
to manage noise.
Ensure that the output buffer current strength is
sufficiently high, but does not cause excessive
overshoot or undershoot that violates voltage
threshold parameters for the I/O standard. Altera
recommends performing an IBIS or SPICE
simulations to determine the right current
strength setting for your specific application. For
a list of standards and settings, refer to the I/O
Features in Stratix V Devices chapter in volume 1
of the Stratix V Device Handbook.
Programmable
Slew Rate Control
Configure each pin for low-noise or high-speed
performance. A faster slew rate provides high
speed transitions. You can use faster slew rates to
improve the available timing margin in
memory-interface applications or when the
output pin has high-capacitive loading. A slow
slew rate can help reduce system noise, but adds
a nominal delay to rising and falling edges. You
can use the slew rate to reduce SSN.
Confirm that your interface meets its performance
requirements if you use slower slew rates. Altera
recommends performing IBIS or SPICE
simulations to determine the right slew rate
setting for your specific application.
Programmable IOE
Delay
Programmable delay chains can ensure zero hold
times, minimize setup times, or increase
clock-to-output times. You can use delays as
deskewing circuitry to ensure that all bits of a bus
have the same delay going into or out of the
device.
This feature helps read and time margins because
it minimizes the uncertainties between signals in
the bus. For delay specifications, refer to the DC
and Switching Characteristics for Stratix V
Devices chapter in volume 3 of the Stratix V
Device Handbook.
Delay chains in the single-ended output buffer can
Programmable
independently control the rising and falling edge
Output Buffer Delay
delays of the output buffer.
You can use delays to adjust the output buffer
duty cycle, compensate channel-to-channel skew,
reduce SSO noise by deliberately introducing
channel-to-channel skew, and improve
high-speed memory-interface timing margins.
Open-Drain Output
When configured as an open-drain, the logic
value of the output is either high-Z or 0. Used in
system-level control signals that can be asserted
by multiple devices in the system.
Typically, an external pull-up resistor is required
to provide logic high.
Bus Hold
Weakly holds the signal on an I/O pin at its last
driven state until the next input signal is present,
using a resistor with a nominal resistance (RBH) of
approximately 7 k . With this feature, you do not
require an external pull-up or pull-down resistor
to hold a signal level when the bus is tri-stated.
The circuitry also pulls non-driven pins away from
the input threshold voltage where noise can cause
unintended high-frequency switching.
If the bus-hold feature is enabled, you cannot use
the programmable pull-up option. Disable the
bus-hold feature if the I/O pin is configured for
differential signals. For the specific sustaining
current driven through this resistor and the
overdrive current used to identify the next driven
input and level for each VCCIO voltage, refer to the
DC and Switching Characteristics for Stratix V
Devices chapter in volume 3 of the Stratix V
Device Handbook.
Programmable
Pull-Up Resistor
Pull-up resistor (typically 25 k) weakly holds the
I/O to the VCCIO level when in user mode. Can be
used with the open-drain output to eliminate the
requirement for an external pull-up resistor.
If the programmable pull-up option is enabled,
you cannot use the bus-hold feature.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
I/O and Clock Planning
Page 33
Table 2. Stratix V I/O Features
Feature
Usage
Guidelines and More Information
On-Chip
Termination (OCT)
Driver-impedance matching provides the I/O
driver with controlled output impedance that
closely matches the impedance of the
transmission line to significantly reduce
reflections. OCT maintains signal quality, saves
board space, and reduces external component
costs. Support for on-chip series (RS) with or
without calibration, parallel (RT) with calibration,
and dynamic series and parallel termination for
single-ended I/O standards and on-chip
differential termination (RD) for differential LVDS
I/O standards.
OCT RS and RT are supported in the same I/O
bank for different I/O standards if they use the
same VCCIO supply voltage. Each I/O in an I/O bank
can be independently configured to support OCT
RS, programmable current strength, or OCT RT.
You cannot configure both OCT RS and
programmable current strength or slew rate
control for the same I/O buffer. Differential OCT
RD is available in all I/O pins. For details about the
support and implementation of this feature, refer
to the I/O Features in Stratix V Devices chapter in
volume 1 of the Stratix V Device Handbook.
Programmable
Pre-Emphasis
Increases the amplitude of the high frequency
component of the output signal, and thus helps to
compensate for the frequency-dependent
attenuation along the transmission line.
Refer to the High-Speed Differential I/O Interfaces
and DPA in Stratix V Devices chapter in volume 1
of the Stratix V Device Handbook.
Programmable
Differential Output
Voltage
Allows you to adjust output eye height to optimize
trace length and power consumption. A higher
VOD swing improves voltage margins at the
receiver end while a smaller VOD swing reduces
power consumption.
Refer to the High-Speed Differential I/O Interfaces
and DPA in Stratix V Devices chapter in volume 1
of the Stratix V Device Handbook.
Dedicated
Differential I/O
SERDES Circuitry
with DPA and
Soft-CDR Support
All the I/Os in Stratix V GX devices and E devices
have built-in SERDES circuitry that supports
high-speed LVDS interfaces at data rates of up to
1.424 Gbps. DPA circuitry automatically chooses
the best phase to compensate the skew between
the source synchronous clock and received serial
data. The soft-CDR mode provides the
opportunity for synchronous/asynchronous
applications for chip-to-chip and short reach
board-to-board applications for SGMII protocols.
If you want to use DPA, enable the feature in the
MegaWizard Plug-In Manager. DPA usage adds
some constraints on the placement of high-speed
differential channels. Refer to the feature
description and placement guidelines in the
High-Speed Differential I/O Interfaces and DPA in
Stratix V Devices chapter in volume 1 of the
Stratix V Device Handbook.
Consider the following checklist items and refer to the appropriate documentation in
Table 2 for detailed guidelines:
Check available device I/O features that can help I/O interfaces: current strength, slew rate, I/O delays,
79. open-drain, bus hold, programmable pull-up resistors, PCI clamping diodes, programmable
pre-emphasis, and VOD.
80. Consider OCT features to save board space.
81. Verify that the required termination scheme is supported for all pin locations.
82. Choose the appropriate mode of DPA, non-DPA, or soft-CDR for high-speed LVDS interfaces.
Clock and PLL Selection
The first stage in planning your clocking scheme is to determine your system clock
requirements. Understand your device’s available clock resources and
correspondingly plan the design clocking scheme. Consider your requirements for
timing performance, and how much logic is driven by a particular clock.
December 2013
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Stratix V Device Design Guidelines
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I/O and Clock Planning
Stratix V devices provide dedicated low-skew and high fan-out routing networks.
They are organized in a hierarchical structure that provides up to 417 unique clock
domains within the device (16 GCLKs + 92 RCLKs + 309 PCLKs). There are up to 28
fractional PLLs per device and up to 18 independently-programmable outputs per
PLL. You can use 16 differential dedicated GCLK input pins or 48 to 56 single-ended
clock inputs.
83. Use the correct dedicated clock pins and routing signals for clock and global control signals.
The dedicated clock pins drive the clock network directly, ensuring lower skew than
other I/O pins. Use the dedicated routing network to have a predictable delay with
less skew for high fan-out signals. You can also use the clock pins and clock network
to drive control signals like asynchronous reset.
84. Use the device fractional PLLs for clock management.
Connect clock inputs to specific PLLs to drive specific low-skew routing networks.
Analyze the global resource availability for each PLL and the PLL availability for each
clock input pin.
Use the following descriptions to help determine which clock networks are
appropriate for the clock signals in your design:
85.
■
The GCLK networks can drive throughout the entire device, serving as low-skew
clock sources for device logic. This clock region has the maximum delay compared
to other clock regions but allows the signal to reach everywhere within the device.
This option is good for routing global reset/clear signals or routing clocks
throughout the device.
■
The RCLK networks only pertain to the quadrant they drive into and provide the
lowest clock delay and skew for logic contained within a single device quadrant.
■
IOEs and internal logic can also drive GCLKs and RCLKs to create internally
generated GCLKs or RCLKs and other high fan-out control signals; for example,
synchronous or asynchronous clears and clock enables.
■
PLLs cannot be driven by internally-generated GCLKs or RCLKs. The input clock
to the PLL must come from dedicated clock input pins or from another
pin/PLL-fed GCLK or RCLK.
■
PCLK networks are a collection of individual clock networks driven from the
periphery of the Stratix V device. Clock outputs from the DPA block,
PLD-transceiver interface, I/O pins, and internal logic can drive the PCLK
networks. These PCLKs have higher skew compared to GCLK and RCLK
networks and can be used instead of general purpose routing to drive signals into
and out of the Stratix V device.
Analyze input and output routing connections for each PLL and clock pin. Ensure PLL inputs come
from the dedicated clock pins or from another PLL.
f For more information about these features and detailed clock connection information,
refer to the Clock Networks and PLLs in Stratix V Devices chapter in volume 1 of the
Stratix V Device Handbook.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
I/O and Clock Planning
Page 35
If your system requires more clock or control signals than are available in the target
device, consider cases where the dedicated clock resource could be spared,
particularly low fan-out and low-frequency signals where clock delay and clock skew
do not have a significant impact on the design performance. Use the Global Signal
assignment in the Quartus II Assignment Editor to select the type of global routing, or
set the assignment to Off to specify that the signal should not use any global routing
resources.
PLL Feature Guidelines
Based on your system requirements, define the required clock frequencies for your
FPGA design, and the input frequencies available to the FPGA. Use these
specifications to determine your PLL scheme. Use the Quartus II MegaWizard Plug-In
Manager to enter your settings in Altera PLL megafunctions, and check the results to
verify whether particular features and input/output frequencies can be implemented
in a particular PLL.
86. Enable PLL features and check settings in the MegaWizard Plug-In Manager.
Stratix V devices contain fractional PLLs in addition to integer PLLs. You can
configure fractional PLLs as integers or as enhanced fractional PLLs. One fractional
PLL can use up to 18 output counters and all external clock outputs. Two adjacent
fractional PLLs share the 18 output counters.
You can use fractional PLLs to reduce the number of oscillators required on the board,
as well as to reduce the clock pins used in the FPGA by synthesizing multiple clock
frequencies from a single reference clock source. In addition, you can use fractional
PLLs for clock network delay compensation, zero-delay buffering, and transmit
clocking for transceivers.
Stratix V device PLLs are feature rich, and support advanced capabilities such as clock
feedback modes, switchover, and dynamic phase shifting.
f For more information about the fractional PLL features, refer to the Clock Networks and
PLLs in Stratix V Devices chapter in volume 1 of the Stratix V Device Handbook.
Clock Feedback Mode
Stratix V PLLs support up to six different clock feedback modes: source synchronous
mode, source synchronous mode for LVDS compensation, direction compensation
mode, normal mode, zero-delay buffer (ZDB) mode, and external-feedback mode.
Each mode allows clock multiplication and division, phase shifting, and
programmable duty cycle. Choose the correct feedback mode for your application.
87.
Ensure you select the correct PLL feedback compensation mode.
Clock Outputs
You can connect clock outputs to dedicated clock output pins or dedicated clock
networks.
88. Check that the PLL offers the required number of clock outputs and use dedicated clock output pins.
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I/O and Clock Planning
Clock Control Block
Every GCLK and RCLK network has its own clock control block. The control block
provides the following features:
■
Clock source selection (with dynamic selection for GCLKs)
■
GCLK multiplexing
■
Clock power down (with static or dynamic clock enable or disable)
Use these features to select different clock input signals or power-down clock
networks to reduce power consumption without using any combinational logic in
your design. In Stratix V devices, the clock enable signals are supported at the clock
network level instead of at the PLL output counter level, so you can turn off a clock
even when a PLL is not being used.
f For information about using the ALTCLKCTRL megafunction to set up the clock
control block, refer to the Clock Control Block Megafunction User Guide (ALTCLKCTRL).
89. Use the clock control block for clock selection and power-down.
I/O Simultaneous Switching Noise
SSN is a concern when too many I/Os (in close proximity) change voltage levels at the
same time. Consider the following checklist recommendations when planning I/O
and clock connections:
90. Analyze the design for possible SSN problems.
91. Reduce the number of pins that switch the voltage level at exactly the same time whenever possible.
92. Use differential I/O standards and lower-voltage standards for high-switching I/Os.
93.
Use lower drive strengths for high-switching I/Os. The default drive strength setting might be higher
than your design requires.
94.
Reduce the number of simultaneously switching output pins within each bank. Spread output pins
across multiple banks if possible.
95.
Spread switching I/Os evenly throughout the bank to reduce the number of aggressors in a given area
to reduce SSN (when bank usage is substantially below 100%).
96. Separate simultaneously switching pins from input pins that are susceptible to SSN.
97.
Place important clock and asynchronous control signals near ground signals and away from large
switching buses.
98.
Avoid using I/O pins one or two pins away from PLL power supply pins for high-switching or
high-drive strength pins.
99.
Use staggered output delays to shift the output signals through time, or use adjustable slew rate
settings.
Refer to “Stratix V I/O Features” on page 31 for details about the features you can use.
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Design Entry
In complex FPGA design development, design practices, coding styles, and
megafunction use have an enormous impact on your device’s timing performance,
logic utilization, and system reliability. In addition, while planning and creating the
design, plan for a hierarchical or team-based design to improve design productivity.
Design Recommendations
In a synchronous design, a clock signal triggers all events. When all of the registers’
timing requirements are met, a synchronous design behaves in a predictable and
reliable manner for all process, voltage, and temperature (PVT) conditions. You can
easily target synchronous designs to different device families or speed grades.
100. Use synchronous design practices. Pay attention to clock signals.
Problems with asynchronous design techniques include reliance on propagation
delays in a device, incomplete timing analysis, and possible glitches. Pay particular
attention to your clock signals, because they have a large effect on your design’s
timing accuracy, performance, and reliability. Problems with clock signals can cause
functional and timing problems in your design. Use dedicated clock pins and clock
routing for best results. For clock inversion, multiplication, and division, use the
device PLLs. For clock multiplexing and gating, use the dedicated clock control block
or PLL clock switchover feature instead of combinational logic. Refer to “PLL Board
Design Guidelines” on page 19. If you must use internally generated clock signals,
register the output of any combinational logic used as a clock signal to reduce
glitches. For example, if you divide a clock using combinational logic, clock the final
stage with the clock signal that was used to clock the divider circuit.
101. Use the Quartus II Design Assistant to check design reliability.
The Design Assistant in the Quartus II software is a design-rule checking tool that
enables you to check for design issues early in the design flow. The Design Assistant
checks your design for adherence to Altera recommended design guidelines or design
rules. To run the Design Assistant, on the Processing menu, point to Start and click
Start Design Assistant. To set the Design Assistant to run automatically during
compilation, turn on Run Design Assistant during compilation in the Settings
dialog box. You can also use third-party “lint” tools to check your coding styles.
f For more information about design recommendations and using the Design Assistant,
refer to the Design Recommendations for Altera Devices and the Quartus II Design
Assistant chapter in volume 1 of the Quartus II Handbook. You can also refer to industry
papers for more information about multiple clock design. For a good analysis, refer to
www.sunburst design.com.
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Design Entry
Using Megafunctions
Altera provides parameterizable megafunctions that are optimized for Altera device
architectures. You can save design time by using megafunctions instead of coding
your own logic. Additionally, the Altera-provided megafunctions can offer more
efficient logic synthesis and device implementation. You can scale the megafunction’s
size and set various options with parameters. Megafunctions include the library of
parameterized modules (LPM) and Altera device-specific megafunctions. You can
also take advantage of Altera and third-party IP and reference designs to save design
time, as described in “IP Selection” on page 3.
The Quartus II MegaWizard Plug-In Manager provides a user interface to customize
megafunctions. You should build or change megafunction parameters using the
MegaWizard Plug-In Manager to ensure you set all ports and parameters correctly.
102. Use megafunctions with the MegaWizard Plug-In Manager.
f For detailed information about specific megafunctions, refer to the Quartus II Help or
the megafunction user guides on the User Guides Literature page.
Reconfiguration
Stratix V devices allow you to easily modify your transceivers and FPGA-core while
other portions of your design are still running by using dynamic reconfiguration and
partial reconfiguration, respectively.
Dynamic Reconfiguration
Stratix V devices allow you to dynamically reconfigure different portions of the
transceivers for different protocols, data rates, and PMA settings without powering
down any part of the device or interrupting adjacent transceiver channels.
f For more information about dynamic reconfiguration, refer to the Dynamic
Reconfiguration in Stratix V Devices chapter in volume 2 of the Stratix V Device
Handbook.
Partial Reconfiguration
Partial reconfiguration is suitable for designs with many permutations that do not
operate simultaneously. In such systems, one section of the FPGA continues to
operate, while the other section is reconfigured for new functionality. Partial
reconfiguration improves logic density by removing the need to implement functions
that do not operate simultaneously in the FPGA and can potentially reduce the device
resource count.
f For more information about partial reconfiguration, refer to the Increasing Design
Functionality with Partial and Dynamic Reconfiguration in 28-nm FPGAs white paper.
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Recommended HDL Coding Styles
HDL coding styles can have a significant effect on the quality of results for
programmable logic designs. Use Altera’s recommended coding styles to achieve
optimal synthesis results. When designing memory and digital system processing
(DSP) functions, it is helpful to understand the device architecture so you can take
advantage of the dedicated logic block sizes and configurations.
103.
Follow recommended coding styles, especially for inferring device dedicated logic such as memory
and DSP blocks.
f For specific HDL coding examples and recommendations, refer to the Recommended
HDL Coding Styles chapter in volume 1 of the Quartus II Handbook. Refer to your
synthesis tool’s documentation for any additional tool-specific guidelines. In the
Quartus II software, you can use the HDL examples in the Language Templates
available from the right-click menu in the text editor.
Register Power-Up Levels and Control Signals
Stratix V devices support an optional chip-wide reset that enables you to override all
clears on all device registers, including the registers of the memory blocks (but not the
memory contents itself). When this DEV_CLRn pin is driven low, all registers are cleared
or reset to 0. If synthesis performs an optimization called NOT-gate-push back due to
register control signals, affected registers behave as though they are preset to a high
value when DEV_CLRn is driven low. When the DEV_CLRn pin is driven high, all
registers behave as programmed. To use this chip-wide reset, turn on Enable
device-wide reset (DEV_CLRn) in the Quartus II software on the General category of
the Device and Pin Options dialog box before compiling your design.
104. Enable the chip-wide reset to clear all registers if required.
Each Stratix V logic array block (LAB) also contains dedicated logic for driving
register control signals to its ALMs. The control signals include three clocks, three
clock enables, two asynchronous clears, a synchronous clear, and a synchronous load.
Register control signals restrict how registers are packed into LABs because signals
are shared within the LAB. It is important that control signals use the dedicated
control signals in the device architecture, so in some cases you might be required to
limit the number of different control signals used in your design.
f For more information about LAB and ALM architecture, refer to the Logic Array Blocks
and Adaptive Logic Modules in Stratix V Devices chapter in volume 1 of the Stratix V
Device Handbook.
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Design Entry
If the clock signal is not available when reset is asserted, an asynchronous reset is
typically used to reset the logic. The recommended reset architecture allows the reset
signal to be asserted asynchronously and de-asserted synchronously. The source of
the reset signal is then connected to the asynchronous port of the registers, which can
be directly connected to global routing resources. The synchronous de-assertion
allows all state machines and registers to start at the same time. It also avoids the
possibility that an asynchronous reset signal is released at or near the active clock
edge of a flipflop, in which case the output of the flipflop could go to a metastable
unknown state.
f You can refer to industry papers for more information about reset design. For good
analysis of reset architecture, refer to: www.sunburst-design.com.
By default, Quartus II integrated synthesis enables the logic option called Power-Up
Don’t Care, which assumes your design does not depend on the power-up state of the
device architecture and allows the software to remove registers that become stuck
high. Other synthesis tools might use similar assumptions.
Designers typically use an explicit reset signal for the design that forces all registers
into their appropriate values after reset but not necessarily at power-up. You can
create your design such that the asynchronous reset allows the board to operate in a
safe condition. You can then bring up the design with the reset active. Thus, you do
not have to depend on the power-up conditions of the device.
If you force a particular power-up condition for your design, use the synthesis options
available in your synthesis tool.
Some synthesis tools can also read the default or initial values for registered signals in
your source code and implement this behavior in the device. For example, Quartus II
integrated synthesis converts HDL default and initial values for registered signals
into Power-Up Level settings. That way, the synthesized behavior matches the
power-up state of the HDL code during a functional simulation.
f The Power-Up Level option and the altera_attribute assignment that set power-up
conditions are described in the Quartus II Integrated Synthesis chapter in volume 1 of
the Quartus II Handbook.
Registers in the device core always power up to a low (0) logic level in the physical
device architecture. If you specify a high power-up level or a non-zero reset value
(often called a preset signal), synthesis tools typically use the clear signals available on
the registers and perform an optimization referred to as NOT-gate push back.
If you assign a high power-up level to a register that is reset low, or assign a low
power-up value to a register that is preset high, synthesis tools cannot use the
NOT-gate push back optimization technique and might ignore the power-up
conditions.
105.
Consider resources available for register power-up and control signals. Do not apply both reset and
preset signals to a register.
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To implement a reset and preset signal on the same register, synthesis tools emulate
the controls with logic and latches that can be prone to glitches because of the
different delays between the different paths to the register. In addition, the power-up
value is undefined for these registers.
f For more information about reset logic and power up conditions, refer to the
Recommended HDL Coding Styles chapter in volume 1 of the Quartus II Handbook.
Planning for Hierarchical and Team-Based Design
The Quartus II incremental compilation feature preserves the results and performance
for unchanged logic in your design as you make changes elsewhere, allowing you to
perform more design iterations and achieve timing closure more efficiently. In an
incremental compilation flow, the system architect splits a large design into smaller
partitions that can be designed separately. In a team design environment, team
members can work on partitions independently, which simplifies the design process
and reduces compilation time. Partitioning your design is optional, but these benefits
are important for large Stratix V designs.
1
The bottom-up design flows are not supported for HardCopy migrations. If you
migrate to a HardCopy V ASIC, use the top-down incremental compilation
methodology with a consistent set of global assignments for all design blocks, so the
same assignments can be recreated in the HardCopy revision.
If you want to take advantage of the compilation-time savings and performance
preservation of Quartus II incremental compilation, plan for an incremental
compilation flow from the beginning of your design cycle. Good partition and
floorplan design helps lower-level design blocks meet top-level design requirements,
reducing the time spent integrating and verifying the timing of the top-level design.
f For more information about using the incremental compilation flows in the Quartus II
software, refer to the Quartus II Incremental Compilation for Hierarchical and Team-Based
Design chapter in volume 1 of the Quartus II Handbook.
Planning Design Partitions
Partitioning a design for an FPGA requires planning to ensure optimal results when
the partitions are integrated and ensures that each partition is well placed, relative to
other partitions in the device.
Follow Altera’s recommendations for creating design partitions to improve the
overall quality of results. For example, registering partition I/O boundaries keeps
critical timing paths inside one partition that can be optimized independently.
Plan your source code so that each design block is defined in a separate file. The
software can automatically detect changes to each block separately. Use hierarchy in
your design to provide more flexibility when partitioning. Keep your design logic in
the leaves of the hierarchy trees; that is, the top level of the hierarchy should have
very little logic, and the lower-level design blocks contain the logic.
106.
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Follow recommendations to set up your source code and partition your design for incremental
compilation; plan early in the design flow.
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f For guidelines to help you create design partitions, refer to the Best Practices for
Incremental Compilation Partitions and Floorplan Assignments chapter in volume 1 of the
Quartus II Handbook.
Planning in Bottom-Up and Team-Based Flows
If your design is created in multiple Quartus II projects, it is important that the system
architect provide guidance to designers of lower-level blocks to ensure that each
partition uses the appropriate device resources. Because the designs are developed
independently, each lower-level designer has no information about the overall design
or how their partition connects with other partitions. This lack of information can lead
to problems during system integration. The top-level project information, including
pin locations, physical constraints, and timing requirements, should be
communicated to the designers of lower-level partitions before they start their design.
107.
Perform timing budgeting and resource balancing between partitions to achieve best results,
especially in team-based flows.
The system architect can plan design partitions at the top level and use the Quartus II
software Generate Bottom-Up Design Partition Scripts option under the Project
menu to automate the process of transferring top-level project information to
lower-level modules.
Creating a Design Floorplan
To take full advantage of incremental compilation, you can create a design floorplan
to avoid conflicts between design partitions, and to ensure that each partition is well
placed relative to other partitions. When you create different location assignments for
each partition, no location conflicts occur. In addition, a design floorplan helps avoid
situations in which the Fitter is directed to place or replace a portion of the design in
an area of the device where most resources have already been claimed. Floorplan
assignments are recommended for timing-critical partitions in top-down flows.
108. Create a design floorplan for incremental compilation partitions, if required for your design flow.
You can use the Quartus II Chip Planner to create a design floorplan using LogicLock
region assignments for each design partition. With a basic design framework for the
top-level design, the floorplan editor enables you to view connections between
regions, estimate physical timing delays on the chip, and move regions around the
device floorplan. When you have compiled the full design, you can also view logic
placement and locate areas of routing congestion to improve the floorplan
assignments.
f For guidelines to help you create a design floorplan, refer to the Best Practices for
Incremental Compilation Partitions and Floorplan Assignments chapter in volume 1 of the
Quartus II Handbook. For more information about creating placement assignments in
the floorplan, refer to the Analyzing and Optimizing the Design Floorplan chapter in
volume 2 of the Quartus II Handbook.
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Design Implementation, Analysis, Optimization, and Verification
After you create your design source code and apply constraints including the device
selection and timing requirements, your synthesis tool processes the code and maps it
to elements of the device architecture. The Quartus II Fitter then performs placement
and routing to implement the design elements in specific device resources. If required,
you can use the Quartus II software to optimize the design’s resource utilization and
achieve timing closure, preserve the performance of unchanged design blocks, and
reduce compilation time for future iterations. You can also verify the design
functionality with simulation or formal verification. This section provides guidelines
for these stages of the compilation flow.
Selecting a Synthesis Tool
The Quartus II software includes advanced and easy-to-use integrated synthesis that
fully supports Verilog HDL and VHDL, as well as the Altera hardware description
language (AHDL) and schematic design entry. You can also use industry-leading
third-party EDA synthesis tools to synthesize your Verilog HDL or VHDL design, and
then compile the resulting output netlist file in the Quartus II software. Specify a
third-party synthesis tool in the New Project Wizard or the EDA Tools Settings page
of the Settings dialog box to use the correct Library Mapping File (.lmf) for your
synthesis netlist.
Altera recommends that you use the most recent version of third-party synthesis
tools, because tool vendors are continuously adding new features, fixing tool issues,
and enhancing performance for Altera devices.
Different synthesis tools can give different results. If you want to select the
best-performing tool for your application, you can experiment by synthesizing typical
designs for your application and coding style and comparing the results. Be sure to
perform placement and routing in the Quartus II software to get accurate timing
analysis and logic utilization results.
109. Specify your third-party synthesis tool and use the correct supported version.
Your synthesis tool might offer the capability to create a Quartus II project and pass
constraints such as the EDA tool setting, device selection, and timing requirements
that you specified in your synthesis project. You can use this capability to save time
when setting up your Quartus II project for placement and routing.
f For more information about supported synthesis tools, refer to the appropriate
chapter in Section III. Synthesis in volume 1 of the Quartus II Handbook. The Quartus II
Software Release Notes list the version of each synthesis tool that is officially supported
by that version of the Quartus II software.
Device Resource Utilization Reports
After compilation in the Quartus II software, review the device resource utilization
information to determine whether the future addition of extra logic or other design
changes introduce fitting difficulties. If your compilation results in a no-fit error,
resource utilization information is important so you can analyze the fitting problems
in your design.
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To determine resource usage, refer to the Flow Summary section of the Compilation
Report for a percentage representing the total logic utilization, which includes an
estimation of resources that cannot be used due to existing connections or logic use.
For Stratix V devices, low logic utilization does not have the lowest ALM utilization
possible. In addition, a design that is reported as close to 100% full might still have
space for extra logic. The Fitter uses ALUTs in different ALMs, even when the logic
can be placed within one ALM, so that it can achieve the best timing and routability
results. Logic might be spread throughout the device when achieving these results. As
the device fills up, the Fitter automatically searches for logic that can be placed
together in one ALM.
More detailed resource information is available by viewing the reports under
Resource Section in the Fitter section of the Compilation Report. The Fitter Resource
Usage Summary report breaks down the logic utilization information and indicates
the number of fully and partially used ALMs, and provides other resource
information including the number of bits in each type of memory block. There are also
reports that describe some of the optimizations that occurred during compilation. For
example, if you use Quartus II integrated synthesis, the reports under the
Optimization Results folder in the Analysis & Synthesis section provide
information, including registers that were removed during synthesis. Use this report
to estimate device resource utilization for a partial design to ensure that registers were
not removed due to missing connections with other parts of the design.
110. Review resource utilization reports after compilation.
Quartus II Messages
Each stage of the compilation flow generates messages, including informational notes,
warnings, and critical warnings. Review these messages to check for any design
problems. Ensure that you understand the significance of any warning messages, and
make changes to the design or settings if required. In the Quartus II user interface,
you can use the Message window tabs to look at only certain types of messages, and
you can suppress messages if you have determined that they do not require any
action from you.
111. Review all Quartus II messages, especially warning or error messages.
f For more information about messages and message suppression, refer to the Managing
Quartus II Projects chapter in volume 2 of the Quartus II Handbook.
Timing Constraints and Analysis
In an FPGA design flow, accurate timing constraints allow timing-driven synthesis
software and place-and-route software to obtain optimal results. Timing constraints
are critical to ensure designs meet their timing requirements, which represent actual
design requirements that must be met for the device to operate correctly. The
Quartus II software optimizes and analyzes your design using different timing
models for each device speed grade, so you must perform timing analysis for the
correct speed grade. The final programmed device might not operate as expected if
the timing paths are not fully constrained, analyzed, and verified to meet
requirements.
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The Quartus II software includes the Quartus II TimeQuest Timing Analyzer, a
powerful ASIC-style timing analysis tool that validates the timing performance of all
logic in your design. It supports the industry standard Synopsys Design Constraints
(SDC) format timing constraints, and has an easy-to-use GUI with interactive timing
reports. It is ideal for constraining high-speed source-synchronous interfaces and
clock multiplexing design structures.
The software also supports static timing analysis in the industry-standard Synopsys
Primetime software. Specify the tool in the New Project Wizard or the EDA Tools
Settings page of the Settings dialog box to generate the required timing netlist.
A comprehensive static timing analysis includes analysis of register to register, I/O,
and asynchronous reset paths. It is important to specify the frequencies and
relationships for all clocks in your design. Use input and output delay constraints to
specify external device or board timing parameters. Specify accurate timing
requirements for external interfacing components to reflect the exact system intent.
The TimeQuest Timing Analyzer performs static timing analysis on the entire system,
using data required times, data arrival times, and clock arrival times to verify circuit
performance and detect possible timing violations. It determines the timing
relationships that must be met for the design to correctly function.
You can use the report_datasheet command to generate a datasheet report that
summarizes the I/O timing characteristics of the entire design.
112. Ensure timing constraints are complete and accurate, including all clock signals and I/O delays.
113.
Review the TimeQuest Timing Analyzer reports after compilation to ensure there are no timing
violations.
114. Ensure that the input I/O times are not violated when data is provided to the Stratix V device.
f For more information about timing analysis, refer to The Quartus II TimeQuest Timing
Analyzer and Synopsys PrimeTime Support chapters in volume 3 of the Quartus II
Handbook.
Recommended Timing Optimization and Analysis Assignments
The assignments and settings described in this section are important for large designs
such as those in Stratix V devices.
115. Turn on Optimize multi-corner timing on the Fitter Settings page in the Settings dialog box.
When the Optimize multi-corner timing option is on, the design is optimized to meet
its timing requirements at all timing process corners and operating conditions.
Therefore, turning on this option helps create a design implementation that is more
robust across PVT variations.
In your TimeQuest Timing Analyzer .sdc constraints file, use the following
recommended constraints as applicable to your design:
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116.
Use create_clock and create_generated_clock to specify the frequencies and relationships for
all clocks in your design.
117.
Use set_input_delay and set_output_delay to specify the external device or board timing
parameters.
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Use derive_pll_clocks to create generated clocks for all PLL outputs, according to the settings in
118. the PLL megafunctions. Specify multicycle relationships for LVDS transmitters or receiver
deserialization factors.
119.
Use derive_clock_uncertainty to automatically apply inter-clock, intra-clock, and I/O interface
uncertainties.
120.
Use check_timing to generate a report on any problem with the design or applied constraints,
including missing constraints.
f For more guidelines about timing constraints, refer to the Best Practices for the
Quartus II TimeQuest Timing Analyzer chapter in volume 3 of the Quartus II Handbook.
Area and Timing Optimization
This section highlights some of the features offered in the Quartus II software to help
optimize area (or resource utilization) and timing performance. If the timing analysis
reports that your design requirements were not met, you must make changes to your
design or settings and recompile the design to achieve timing closure. If your
compilation results in no-fit messages, you must make changes to get successful
placement and routing.
f For information about additional optimization features, refer to the Area and Timing
Optimization chapter in volume 2 of the Quartus II Handbook.
You can use the Early Timing Estimation feature to estimate your design’s timing
results before the software performs full placement and routing. On the Processing
menu, point to Start and click Start Early Timing Estimate to generate initial
compilation results after you have run analysis and synthesis.
121. Perform Early Timing Estimation if you want timing estimates before running a full compilation.
Physical synthesis optimizations make placement-specific changes to the netlist that
improve results for a specific Altera device. You can optimize for performance and
fitting in the Physical Synthesis Optimizations page of the Settings dialog box. The
options in the Physical Synthesis Optimizations page typically increase compilation
time significantly but can provide significant improvements to the quality of results
with push-button optimizations. If you turn on these options, ensure that they do
improve the results for your design. If you do not require these options to meet your
design timing requirements, turn off the options to reduce the compilation time.
f For more information, refer to the Netlist Optimizations and Physical Synthesis chapter
in volume 2 of the Quartus II Handbook.
The Design Space Explorer (DSE) is a utility that automates the process of finding the
optimal collection of Quartus II software settings for your design. The Search for Best
Performance and Search for Best Area options under Exploration Settings use a
predefined exploration space to target design performance or area improvements
with multiple compilations. You can also set the Optimization Goal to Optimize for
Speed or Optimize for Area using the Advanced tab in the DSE window. If you are
interested in optimization for power usage, refer to “Power Optimization” on
page 50.
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h For more information, refer to About Design Space Explorer in the Quartus II Help.
The Optimization Advisors provide guidance in making settings that optimize your
design. On the Tools menu, point to Advisors and click Resource Optimization
Advisor or Timing Optimization Advisor. Evaluate the options and choose the
settings that best suit your requirements.
122. Use Quartus II optimization features to achieve timing closure or improve the resource utilization.
123. Use the Timing and Area Optimization Advisors to suggest optimization settings.
Preserving Performance and Reducing Compilation Time
Use the incremental compilation feature to preserve logic in unchanged parts of your
design, preserve timing performance, and reach timing closure more efficiently. You
can speed up design iteration time by an average of 60% when making changes to the
design with the incremental compilation feature.
124.
Use incremental compilation to preserve performance for unchanged blocks in your design and to
reduce compilation times.
For guidelines and references, refer to “Planning for Hierarchical and Team-Based
Design” on page 41.
125. Ensure parallel compilation is enabled if you have multiple processors available for compilation.
The Quartus II software can run some algorithms in parallel to take advantage of
multiple processors and reduce compilation time when more than one processor is
available to compile the design. Set the Parallel compilation option on the
Compilation Process Settings page of the Settings dialog box, or change the default
setting in the Options dialog box in the Processing page from the Tools menu.
126. Use the Compilation Time Advisor to suggest settings that reduce compilation time.
The Compilation Time Advisor provides guidance in making settings that reduce
your design compilation time. On the Tools menu, point to Advisors and click
Compilation Time Advisor. Using some of these techniques to reduce compilation
time can reduce the overall quality of results.
f For more suggestions, refer to the Area and Timing Optimization chapter in volume 2 of
the Quartus II Handbook.
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Simulation
The Quartus II software supports both functional and gate-level timing simulations.
Perform functional simulation at the beginning of your design flow to check the
design functionality or logical behavior of each design block. You do not have to fully
compile your design; you can generate a functional simulation netlist that does not
contain timing information. Timing simulation uses the timing netlist generated by
the TimeQuest Timing Analyzer, including the delay of different device blocks and
placement and routing information. You can perform timing simulation for the
top-level design at the end of your design flow to ensure that your design works in
the targeted device.
Altera provides the ModelSim®-Altera simulator Starter Edition and offers the
higher-performance ModelSim-Altera Edition, which enable you to take advantage of
advanced testbench capabilities and other features. In addition, the Quartus II EDA
Netlist Writer can generate timing netlist files to support other third-party simulation
tools such as Synopsys VCS, Cadence NC-Sim, and Aldec Active-HDL. Specify your
simulation tool in the EDA Tools Settings page of the Settings dialog box to generate
the appropriate output simulation netlist. The software can also generate scripts to
help you setup libraries in your tool with NativeLink integration.
127.
Specify your third-party simulation tool, and use the correct supported version and simulation
models.
If you use a third-party simulation tool, use the software version that is supported
with your Quartus II software version. The Quartus II Software Release Notes list the
version of each simulation tool that is officially supported with that particular version
of the Quartus II software. Use the model libraries provided with your Quartus II
software version, because libraries can change between versions, which might cause a
mismatch with your simulation netlist. To create a testbench, on the Processing menu,
point to Start and click Start Testbench Template Writer.
f For more information about simulation tool flows, refer to the appropriate chapter in
Section I. Simulation in volume 3 of the Quartus II Handbook.
Formal Verification
The Quartus II software supports some formal verification flows. Using a formal
verification flow can impact performance results because it requires that certain logic
optimizations be turned off, such as register retiming, and forces hierarchy blocks to
be preserved, which can restrict optimization. There are other restrictions that can also
limit your design; consult the documentation for details.
f For more information about formal verification flows, refer to Section V. Formal
Verification in volume 3 of the Quartus II Handbook.
If formal verification is important to your design, it is easier to plan for limitations
and restrictions in the beginning than to make changes later in the design flow.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Design Implementation, Analysis, Optimization, and Verification
Page 49
The Quartus II Software Release Notes list the version of each formal verification tool
that is officially supported with that particular version of the Quartus II software.
Specify your formal verification tool in the EDA Tools Settings page of the Settings
dialog box to generate the appropriate output netlist.
128.
Specify your third-party formal verification tool and use the correct supported version.
129.
If you use formal verification, check for support and design limitations.
Power Analysis
Before design completion, estimate power consumption using a spreadsheet as
described in “Early Power Estimation” on page 8. After compiling your design,
analyze the power consumption and heat dissipation with the Quartus II PowerPlay
Power Analyzer to ensure the design has not violated power supply and thermal
budgets.
130. After compilation, analyze power consumption and heat dissipation in the PowerPlay Power Analyzer.
131.
Provide accurate typical signal activities, preferably with a gate-level simulation .vcd, to get accurate
power analysis results.
You must compile a design (to provide information about design resources,
placement and routing, and I/O standards) and provide signal activity data (toggle
rates and static probabilities) to use the PowerPlay Power Analyzer. You can derive
signal activity data from simulation results or a user-defined default toggle rate and
vectorless estimation. The signal activities used for analysis must be representative of
the actual operating behavior. For the most accurate power estimation, use gate-level
simulation results with a .vcd output file from a third-party simulation tool. The
simulation activity should include typical input vectors over a realistic time period
and not the corner cases often used during functional verification. Use the
recommended simulator settings (such as glitch filtering) to ensure good results. Refer
to “Simulation” for information about third-party simulators.
132. Specify the correct operating conditions for power analysis.
You must also specify operating conditions, including the core voltage, device power
characteristics, ambient and junction temperature, cooling solution, and the board
thermal model. Select the appropriate settings on the Operating Settings and
Conditions page in the Settings dialog box.
To calculate the dynamic, static, and I/O thermal power consumption, on the
Processing menu, click PowerPlay Power Analyzer Tool. The tool also provides a
summary of the signal activities used for analysis and a confidence metric that reflects
the overall quality of the data sources for signal activities.
1
The report is a power estimate based on the data provided, and is not a power
specification. Always refer to the datasheet for the power specification of your device.
f For more information about power analysis and recommendations for simulation
settings for creating signal activity information, refer to the PowerPlay Power Analyzer
chapter in volume 3 of the Quartus II Handbook.
December 2013
Altera Corporation
Stratix V Device Design Guidelines
Page 50
Design Implementation, Analysis, Optimization, and Verification
Power Optimization
Stratix V devices utilize advanced process and circuit techniques, along with major
circuit and architecture innovations, to minimize power and deliver high
performance. The Programmable Power Technology feature enables every
programmable LAB, DSP block, and memory block to deliver either high speed or
low power, depending on your design requirements. The Quartus II software
automatically takes advantage of the excess slack found on non-critical design paths
to minimize power consumption while maintaining high performance for critical
paths.
To reduce dynamic power consumption in Stratix V devices, you can use various
design and software techniques to optimize your design.
Power optimization in the Quartus II software depends on accurate power analysis
results. Use the guidelines in the previous section to ensure the software optimizes the
power utilization correctly for the design’s operating behavior and conditions.
Device and Design Power Optimization Techniques
This section lists several design techniques that can reduce power consumption. The
results of these techniques are different from design to design.
133.
Use recommended design techniques and Quartus II options to optimize your design for power
consumption, if required.
134. Use the Power Optimization Advisor to suggest optimization settings.
f For more details and additional design techniques to reduce power consumption,
refer to the Power Optimization chapter in volume 2 of the Quartus II Handbook.
Device Speed Grade
If your design includes many critical timing paths that require the high-performance
mode, you might be able to reduce power consumption by using a faster speed grade
device if available. With a faster device, the software might be able to set more device
tiles to use the low-power mode.
Clock Power Management
Clocks represent a significant portion of dynamic power consumption, because of
their high switching activity and long paths. The Quartus II software automatically
optimizes clock routing power by enabling only the portions of a clock network that
are required to feed downstream registers. You can also use clock control blocks to
dynamically enable or disable the clock network. When a clock network is powered
down, all the logic fed by that clock network does not toggle, thereby reducing the
overall power consumption of the device.
f For more information about using clock control blocks, refer to the Clock Control Block
Megafunction User Guide (ALTCLKCTRL).
To reduce LAB-wide clock power consumption without disabling the entire clock tree,
use the LAB-wide clock enable signal to gate the LAB wide clock. The Quartus II
software automatically promotes register-level clock enable signals to the LAB level.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Design Implementation, Analysis, Optimization, and Verification
Page 51
Memory Power Reduction
Reduce the number of memory clocking events to reduce memory power
consumption. You can use clock gating described in “Clock Power Management” or
the clock enable signals in the memory ports.
I/O Power Guidelines
The dynamic power consumed in the I/O buffer is proportional to the total load
capacitance; therefore, lower capacitance reduces power consumption.
Non-terminated I/O standards such as LVTTL and LVCMOS have a rail to-rail output
swing equal to the VCCIO supply voltage. Because dynamic power is proportional to
the square of the voltage, use lower voltage I/O standards to reduce dynamic power.
These I/O standards consume little static power.
Because dynamic power is also proportional to the output transition frequency, use
resistively-terminated I/O standards such as SSTL for high-frequency applications.
The output load voltage swings by a amount smaller than the VCCIO around a bias
point; therefore, dynamic power is lower than for non-terminated I/O under similar
conditions.
Resistively-terminated I/O standards dissipate significant static power because
current is constantly driven into the termination network. Use the lowest drive
strength that meets your speed and waveform requirements to minimize static power
when using resistively terminated I/O standards.
1
The power used by external devices is not included in the PowerPlay calculations, so
be sure to include it separately in your system power calculations.
Quartus II Power Optimization Techniques
The Quartus II software offers power-optimized synthesis and fitting to reduce core
dynamic power. Power-driven compilation works in conjunction with Programmable
Power Technology in Stratix V silicon.
Optimizing your design for area also saves power because fewer logic blocks are
used; therefore, there is typically less switching activity. Improving your design
source code to optimize for performance can also reduce power usage because more
of the design might be placed using low power tiles instead of requiring the
high-performance mode. You can use the DSE and Power Optimization Advisor to
provide additional suggestions to reduce power.
f For more information about power-driven compilation and the Power Optimization
Advisor, refer to the Power Optimization chapter in volume 2 of the Quartus II
Handbook.
Power Optimization Advisor
The Quartus II software includes the Power Optimization Advisor, which provides
specific power optimization advice and recommendations based on the current
design project settings and assignments. On the Tools menu, point to Advisors and
click Power Optimization Advisor. After making any of the recommended changes,
recompile your design and run the Power Play Power Analyzer to check the change in
your power results.
December 2013
Altera Corporation
Stratix V Device Design Guidelines
Page 52
Conclusion
Conclusion
The design guidelines in this application note provide important factors to consider in
high-density, high-performance Stratix V designs. It is important to follow Altera’s
recommendations throughout the design process to achieve good results, avoid
common issues, and improve your design productivity. The “Design Checklist” on
page 53 summarizes the checklist items presented in this document. You can use this
separate checklist to ensure that you have reviewed all the guidelines before
completing your Stratix V design.
Document Revision History
Table 3 shows the revision history for this document.
Table 3. Document Revision History
Date
Version
Changes
December 2013
1.1
Updated the “Device Power-Up” section.
December 2010
1.0
Initial release.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Design Checklist
Page 53
Design Checklist
Use the checklist to verify that you have followed the guidelines for each stage of your
design.
Done N/A
1.

“Create detailed design specifications and a test plan if appropriate.”
2.

“Plan clock domains, clock resources, and I/O interfaces early with a block diagram.”
3.

“Select IP that affects system design, especially I/O interfaces.”
4.

“If you plan to use the OpenCore Plus tethered mode for IP, ensure that your board design supports this mode
of operation.”
5.

“Take advantage of the SOPC Builder for system and processor designs.”
6.

“Select a device based on transceivers, I/O pin count, LVDS channels, package offering,
logic/memory/multiplier density, PLLs, clock routing, and speed grade.”
7.

“Reserve device resources for future development and debugging.”
8.

“Consider vertical device migration availability and requirements.”
9.

“If you want to migrate to a HardCopy V ASIC, review the appropriate design considerations.”
10.

“Estimate power consumption with the PowerPlay Early Power Estimator (EPE) spreadsheet to plan the
cooling solution and power supplies before the logic design is complete.”
11.

“Set up the temperature sensing diode in your design to measure the device junction temperature for thermal
management.”
12.

“Select a configuration scheme to plan companion devices and board connections.”
13.

“If you want to use the AS configuration mode with large device densities, confirm there is a configuration
device available that is large enough for your target FPGA density.”
14.

“If you want to use a flash device with the parallel flash loader, check the list of supported devices.”
15.

“Ensure your configuration scheme and board support the following required features: data decompression,
design security, remote upgrades, single event updates (SEU) mitigation.”
16.

“Plan the board design to support optional configuration pins CLKUSR and INIT_DONE, as required.”
17.

“Plan board design to use the Auto-restart after configuration error option.”
18.

“Take advantage of on-chip debugging features to analyze internal signals and perform advanced debugging
techniques.”
19.

“Select on-chip debugging scheme(s) early to plan memory and logic requirements, I/O pin connections, and
board connections.”
20.

“If you want to use SignalProbe incremental routing, the SignalTap II Embedded Logic Analyzer, Logic
Analyzer Interface, In-System Memory Content Editor, In-System Sources and Probes, or Virtual JTAG
megafunction, plan your system and board with JTAG connections that are available for debugging.”
December 2013
Altera Corporation
Stratix V Device Design Guidelines
Page 54
Design Checklist
21.

“Plan for the small amount of additional logic resources used to implement the JTAG hub logic for JTAG
debugging features.”
22.

“For debugging with the SignalTap II Embedded Logic Analyzer, reserve device memory resources to capture
data during system operation.”
23.

“Reserve I/O pins for debugging with SignalProbe or the Logic Analyzer Interface so you do not have to
change the design or board to accommodate debugging signals later.”
24.

“Ensure the board supports a debugging mode where debugging signals do not affect system operation.”
25.

“Incorporate a pin header or mictor connector as required for an external logic analyzer or mixed signal
oscilloscope.”
26.

“To use debug tools incrementally and reduce compilation time, ensure incremental compilation is on so you
do not have to recompile the design to modify the debug tool.”
27.

“To use the Virtual JTAG megafunction for custom debugging applications, instantiate it in the HDL code as
part of the design process.”
28.

“To use the In-System Sources and Probes feature, instantiate the megafunction in the HDL code.”
29.

“To use the In-System Memory Content Editor for RAM or ROM blocks or the LPM_CONSTANT megafunction,
turn on the Allow In-System Memory Content Editor to capture and update content independently of the
system clock option for the memory block in the MegaWizard™ Plug-In Manager.”
30.

“Design board for power-up: Stratix V output buffers are tri-stated until the device is configured and
configuration pins drive out.”
31.

“Design voltage power supply ramps to be monotonic.”
32.

“Set POR time to ensure power supplies are stable.”
33.

“Design power sequencing and voltage regulators for best device reliability. Connect the GND between boards
before connecting the power supplies.”
34.

“Connect all power pins correctly as specified in the Stratix V Device Family Pin Connection Guidelines.”
35.

“Connect VCCIO pins and VREF pins to support each bank’s I/O standards.”
36.

“Connect the VCCPD pin to 3.0 V for a 3.0-V VCCIO, and 2.5 V for lower I/O voltages.”
37.

“Explore unique requirements for FPGA power pins or other power pins on your board, and determine which
devices on your board can share a power rail.”
38.

“Follow the suggested power supply sharing and isolation guidance, and the specific guidelines for each pin in
the Stratix V Device Family Pin Connection Guidelines.”
39.

“Use the PDN tool to plan your power distribution netlist and decoupling capacitors.”
40.

“Connect all PLL power pins to reduce noise even if the design does not use all the PLLs. For pin voltage
requirements, refer to the Stratix V Device Family Pin Connection Guidelines.”
41.

“Power supply nets should be provided by an isolated power plane, a power plane cut out, or thick trace of at
least 20 mils.”
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Design Checklist
Page 55
42.

“Check that all configuration pin connections and pull-up/pull-down resistors are set correctly for your
configuration scheme(s).”
43.

“Design configuration DCLK and TCK pins to be noise-free.”
44.

“Connect JTAG pins to a stable voltage level if not in use.”
45.

“Connect JTAG pins correctly to the download cable header. Ensure the pin order is not reversed.”
46.

“To disable the JTAG state machine during power-up, pull the TCK pin low through a 1-k resistor to ensure
that an unexpected rising edge does not occur on TCK.”
47.

“Pull TMS and TDI high through a 1-k to 10-k resistor.”
48.

“Connect TRST directly to VCCPD (Connecting the pin low disables the JTAG circuitry).”
49.

“Because the download cable interfaces with the JTAG pins of your device, ensure the download cable and
JTAG pin voltages are compatible.”
50.

“Buffer JTAG signals per the recommendations, especially for connectors or if the cable drives more than
three devices.”
51.

“If your device is in a configuration chain, ensure all devices in the chain are connected properly.”
52.

“Connect the MSEL pins to a select configuration scheme; do not leave them floating. For flexibility to change
between configuration modes during testing or debugging, set up the board to connect each pin to either
VCCPGM or GND without pull-up or pull-down resistors.”
53.

“Connect nIO_PULLUP directly to GND.”
54.

“Hold the nCE (chip enable) pin low during configuration, initialization, and user mode.”
55.

“Turn on the device-wide output enable option, if required.”
56.

“Specify the reserved state for unused I/O pins.”
57.

“Carefully check the pin connections in the Quartus II software-generated .pin. Do not connect RESERVED
pins.”
58.

“Design VREF pins to be noise-free.”
59.

“Break out large bus signals on board layers close to the device to reduce cross talk.”
60.

“Route traces orthogonally if two signal layers are next to each other, if possible. Use a separation of 2 to 3
times the trace width.”
61.

“Check I/O termination and impedance matching for chosen I/O standards, especially for voltage-referenced
standards.”
62.

“Perform board-level simulation using IBIS models (when available).”
63.

“Configure board trace models for Quartus II advanced I/O timing analysis.”
64.

“Use the Quartus II Pin Planner to make pin assignments.”
65.

“Use Quartus II Fitter messages and reports for sign-off of pin assignments.”
December 2013
Altera Corporation
Stratix V Device Design Guidelines
Page 56
Design Checklist
66.

“Verify that the Quartus II pin assignments match those in the schematic and board layout tools.”
67.

“Use the Create Top-Level Design File command with I/O Assignment Analysis to check the I/O assignments
before the design is complete.”
68.

“Plan the I/O signaling type based on the system requirements.”
69.

“Allow the software to assign locations for the negative pin in differential pin pairs.”
70.

“Select a suitable signaling type and I/O standard for each I/O pin.”
71.

“Ensure that the appropriate I/O standard support is supported in the targeted I/O bank.”
72.

“Place I/O pins that share voltage levels in the same I/O bank.”
73.

“Verify that all output signals in each I/O bank are intended to drive out at the bank’s VCCIO voltage level.”
74.

“Verify that all voltage-referenced signals in each I/O bank are intended to use the bank’s VREF voltage level.”
75.

“Check the I/O bank support for LVDS and transceiver features.”
76.

“Use the UniPHY megafunction (or IP core) for each memory interface, and follow connection
guidelines/restrictions in the appropriate documentation.”
77.

“Use dedicated DQ/DQS pins and DQ groups for memory interfaces.”
78.

“Make dual-purpose pin settings and check for any restrictions when using these pins as regular I/O.”
79.

“Check available device I/O features that can help I/O interfaces: current strength, slew rate, I/O delays, opendrain, bus hold, programmable pull-up resistors, PCI clamping diodes, programmable pre-emphasis, and
VOD.”
80.

“Consider OCT features to save board space.”
81.

“Verify that the required termination scheme is supported for all pin locations.”
82.

“Choose the appropriate mode of DPA, non-DPA, or soft-CDR for high-speed LVDS interfaces.”
83.

“Use the correct dedicated clock pins and routing signals for clock and global control signals.”
84.

“Use the device fractional PLLs for clock management.”
85.

“Analyze input and output routing connections for each PLL and clock pin. Ensure PLL inputs come from the
dedicated clock pins or from another PLL.”
86.

“Enable PLL features and check settings in the MegaWizard Plug-In Manager.”
87.

“Ensure you select the correct PLL feedback compensation mode.”
88.

“Check that the PLL offers the required number of clock outputs and use dedicated clock output pins.”
89.

“Use the clock control block for clock selection and power-down.”
90.

“Analyze the design for possible SSN problems.”
91.

“Reduce the number of pins that switch the voltage level at exactly the same time whenever possible.”
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Design Checklist
Page 57
92.

“Use differential I/O standards and lower-voltage standards for high-switching I/Os.”
93.

“Use lower drive strengths for high-switching I/Os. The default drive strength setting might be higher than
your design requires.”
94.

“Reduce the number of simultaneously switching output pins within each bank. Spread output pins across
multiple banks if possible.”
95.

“Spread switching I/Os evenly throughout the bank to reduce the number of aggressors in a given area to
reduce SSN (when bank usage is substantially below 100%).”
96.

“Separate simultaneously switching pins from input pins that are susceptible to SSN.”
97.

“Place important clock and asynchronous control signals near ground signals and away from large switching
buses.”
98.

“Avoid using I/O pins one or two pins away from PLL power supply pins for high-switching or high-drive
strength pins.”
99.

“Use staggered output delays to shift the output signals through time, or use adjustable slew rate settings.”
100.

“Use synchronous design practices. Pay attention to clock signals.”
101.

“Use the Quartus II Design Assistant to check design reliability.”
102.

“Use megafunctions with the MegaWizard Plug-In Manager.”
103.

“Follow recommended coding styles, especially for inferring device dedicated logic such as memory and DSP
blocks.”
104.

“Enable the chip-wide reset to clear all registers if required.”
105.

“Consider resources available for register power-up and control signals. Do not apply both reset and preset
signals to a register.”
106.

“Follow recommendations to set up your source code and partition your design for incremental compilation;
plan early in the design flow.”
107.

“Perform timing budgeting and resource balancing between partitions to achieve best results, especially in
team-based flows.”
108.

“Create a design floorplan for incremental compilation partitions, if required for your design flow.”
109.

“Specify your third-party synthesis tool and use the correct supported version.”
110.

“Review resource utilization reports after compilation.”
111.

“Review all Quartus II messages, especially warning or error messages.”
112.

“Ensure timing constraints are complete and accurate, including all clock signals and I/O delays.”
113.

“Review the TimeQuest Timing Analyzer reports after compilation to ensure there are no timing violations.”
114.

“Ensure that the input I/O times are not violated when data is provided to the Stratix V device.”
115.

“Turn on Optimize multi-corner timing on the Fitter Settings page in the Settings dialog box.”
December 2013
Altera Corporation
Stratix V Device Design Guidelines
Page 58
Design Checklist
116.

“Use create_clock and create_generated_clock to specify the frequencies and relationships for all
clocks in your design.”
117.

“Use set_input_delay and set_output_delay to specify the external device or board timing parameters.”
118.

“Use derive_pll_clocks to create generated clocks for all PLL outputs, according to the settings in the PLL
megafunctions. Specify multicycle relationships for LVDS transmitters or receiver deserialization factors.”
119.

“Use derive_clock_uncertainty to automatically apply inter-clock, intra-clock, and I/O interface
uncertainties.”
120.

“Use check_timing to generate a report on any problem with the design or applied constraints, including
missing constraints.”
121.

“Perform Early Timing Estimation if you want timing estimates before running a full compilation.”
122.

“Use Quartus II optimization features to achieve timing closure or improve the resource utilization.”
123.

“Use the Timing and Area Optimization Advisors to suggest optimization settings.”
124.

“Use incremental compilation to preserve performance for unchanged blocks in your design and to reduce
compilation times.”
125.

“Ensure parallel compilation is enabled if you have multiple processors available for compilation.”
126.

“Use the Compilation Time Advisor to suggest settings that reduce compilation time.”
127.

“Specify your third-party simulation tool, and use the correct supported version and simulation models.”
128.

“Specify your third-party formal verification tool and use the correct supported version.”
129.

“If you use formal verification, check for support and design limitations.”
130.

“After compilation, analyze power consumption and heat dissipation in the PowerPlay Power Analyzer.”
131.

“Provide accurate typical signal activities, preferably with a gate-level simulation .vcd, to get accurate power
analysis results.”
132.

“Specify the correct operating conditions for power analysis.”
133.

“Use recommended design techniques and Quartus II options to optimize your design for power
consumption, if required.”
134.

“Use the Power Optimization Advisor to suggest optimization settings.”
Stratix V Device Design Guidelines
December 2013 Altera Corporation
Appendix: Stratix V Transceiver Design Guidelines
Page 59
Appendix: Stratix V Transceiver Design Guidelines
Quartus II software support for Stratix V transceivers is different from previous
transceiver support models because it accounts for how designers use processors to
handle data flow. High-speed transceivers are represented in the software by PHY IP
cores. The PHY IP cores are missing transceiver voltage, and termination and PLL
settings which are now handled by the Quartus II Settings File (.qsf). This section
describes the requirements for simulating a transceiver design using the custom PHY
IP core, moving to a design, and how to change settings in the .qsf.
f For more information about Stratix V transceivers, refer to the following documents:
December 2013
■
Altera Transceiver PHY IP Core User Guide—This document contains information
about the transceiver PHY IP options. It also contains a getting started section
describing the design flow options: custom Avalon master or Qsys. The Qsys
option is not supported for the high-speed transceiver PHY IP in the ADCS
version 10.1.
■
Stratix V Device Handbook, Volume 2: Transceiver—Volume 2 of the Stratix V Device
Handbook describes how the transceiver features work and the features supported
in protocol specific PHY IP.
■
Avalon Interface Specifications—PHY IP design is modular and uses standard
interfaces. All PHY IPs include an Avalon® Memory-Mapped (Avalon-MM)
interface or conduit interface to access the control and status registers, and an
Avalon Streaming (Avalon-ST) interface to connect to the MAC layer design for
data transfer. This document discusses the Avalon-MM and Avalon-ST protocols,
including timing diagrams.
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Stratix V Device Design Guidelines
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Appendix: Stratix V Transceiver Design Guidelines
What is in the PHY IP?
In previous devices containing transceivers, the user had to build the transceiver
PMA and PCS blocks, the reconfiguration clock, offset cancellation, status and control
block, and the reset timing block for each transceiver group instantiation. In the PHY
IP, these all are in the same instantiation (Figure 2).
Figure 2. Altera Modular PHY Design
PHY - Stratix V Device
PCS
Avalon-ST
TX and RX
PMA
RX Deserializer
To MAC
To HSSI Pins
TX Deserializer
PLL
Reset
Controller
CDR
PCS and PMA Control and Status
Register Memory Map
S
To
Embedded
Controller
Avalon-MM PHY
Management
Avalon-MM
Control and Status
S
Transceiver
Reconfiguration
S
M
Read and Write
Control and Status
Registers
Offset Cancellation
Analog Settings
Hard Logic for Stratix V
M
Avalon-MM Master Interface
Soft Logic for Stratix V
S
Avalon-MM Slave Interface
The control and status registers store device-dependent information about the PCS
and PMA modules. You can access the device-dependent information with the device
independent Avalon-MM interface, reducing overall complexity of the design and the
number of device-dependent signals that you must expose in your top-level module.
The Avalon-MM interface is a synchronous protocol. Each Avalon-MM port is
synchronized with an associated clock interface. A design that interfaces with the
Avalon-MM can include an embedded controller with an Avalon-MM master
interface, a state machine, or µ-controller (simulation model). An Avalon-MM master
is required for each PHY IP core instantiation.
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Appendix: Stratix V Transceiver Design Guidelines
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The transceiver reconfiguration control and reset control are managed by the
Avalon-MM interface. The reset controller manages the rx_analogreset,
rx_digitalreset, tx_digitalreset, and pll_powerdown signals. The reconfiguration
controller controls the writes and reads.
f For information about the addresses of the Avalon-MM registers and the
corresponding register name and description, refer to the Altera Transceiver PHY IP
Core User Guide.
All addressing is in the form of 32-bit registers. Table 5 has a few of the addresses for
custom PHY IP. To address these registers, note which registers are for direct
addressing (have a <n> in the description in the Altera Transceiver PHY IP Core User
Guide) or indirect addressing.
Simulating a Stratix V Design
Create a design. The custom PHY IP in a matching top level with the register map
addressing of the Avalon master is handled by the simulator test bench file.
For this example, a custom PHY IP is used with one duplex channel, 8B/10B is
enabled, and the interface to the FPGA fabric is 8 bits. The 8B/10B status ports are
enabled (Figure 3). The automatic synchronization state machine with the default
settings is used with the word aligner, but the status ports are enabled and the pattern
length is 10.
Figure 3. Custom PHY
Custom PHY
phy_mgmt_clk
phy_mgmt_clk_reset
phy_mgmt_readdata[31..0]
phy_mgmt_waitrequest
phy_mgmt_address[8..0]
tx_ready
phy_mgmt_read
rx_ready
phy_mgmt_write
phy_mgmt_writedata[31..0]
pll_ref_clk
rx_serial_data
rx_parallel_data[7..0]
tx_datak
pll_locked
tx_serial data
rx_runningdisp
rx_disperr
rx_errdetect
rx_syncstatus
tx_clkout
rx_clkout
rx_parallel_data[7..0]
rx_datak
When the custom PHY IP MegaWizard Plug-In Manager is finished, the software
creates two directories in the project directory: <PHY IP name> and <PHY IP
name>_sim.
If you called the IP “customphy,” then the customphy directory has the Quartus II
synthesis files. The customphy_sim\altera_xcvr_custom_phy directory has the
simulation files. These directories can be the same files but they do not have to match
and they are auto generated by the PHY IP MegaWizard Plug-In Manager.
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Appendix: Stratix V Transceiver Design Guidelines
An example tcl script in the customphy_sim\altera_xcvr_custom_phy directory is
auto generated to show how to run a transceiver in the ModelSim simulation. Change
the name of the tcl script for your project. If you plan to run it from the equivalent
directory (custom_phy_sim\altera_xcvr_custom_phy), make a change in the tcl
script at row 51 to point to your Quartus II directory and your project names. For
example, Table 4 shows the required changes for this project:
Table 4. Changes to the tcl Script
#set QUARTUS_ROOTDIR $env(QUARTUS_ROOTDIR)
Original
# dut_name = top-level Verilog variant name as generated by Qmegawiz
#set tb_name <top level Verilog/VHDL testbench name>
set QUARTUS_ROOTDIR C:/altera/10.1/quartus/
set dut_name CustomPHY
set tb_name TopLevel_tb
New
1
The files generated by the PHY IP MegaWizard Plug-In Manager are overwritten the
next time the PHY IP is modified in the MegaWizard Plug-In Manager. If a
modification is required in any of the files for a custom design, the name of the files
should be modified so that they are not overwritten accidentally.
Create a top file design and bring out all the signals to the top level. The top level
matches the custom PHY IP signals.
Figure 4. TOP Level Design
Top Level
phy_mgmt_clk
phy_mgmt_clk_reset
phy_mgmt_readdata[31..0]
phy_mgmt_waitrequest
phy_mgmt_address[8..0]
tx_ready
phy_mgmt_read
rx_ready
phy_mgmt_write
pll_locked
phy_mgmt_writedata[31..0]
tx_serial data
pll_ref_clk
rx_runningdisp
rx_serial_data
rx_disperr
rx_parallel_data[7..0]
rx_errdetect
tx_datak
rx_patterndetect
rx_syncstatus
tx_clkout
rx_clkout
rx_parallel_data[7..0]
rx_datak
Create a test bench (TopLevel_tb) with the following:
■
A clock generator for the phy_mgmt_clk
■
A clock generator for the transceiver refclk (pll_ref_clk)
■
A data generator for the transmit parallel side (plus required align pattern)
■
Plan to use a required memory map control and status registers
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December 2013 Altera Corporation
Appendix: Stratix V Transceiver Design Guidelines
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Working with the Interface
You can run your design, test bench, and tcl script in ModelSim and simulate the
transceiver interface. Verified the details for the interface using the Altera Transceiver
PHY IP Core User Guide. Table 5 lists the registers tested in this exercise.
Table 5. CUSTOM PHY IP CORE REGISTER MAP
Signal
Word Address
Bit
pma_tx_pll_is_locked
h022
—
reset_ch_bitmask
h041
—
reset_control
h042;
—
reset_fine_control
h044;
31-4,0
reset_tx_digital
h044;
1 only
reset_rx_analog
h044;
2 only
Reset_rx_digital
h044;
3 only
phy_serial_loopback
h061;
—
pma_rx_signaldetect
h063;
—
pma_rx_is_lockedtodata
h066;
—
pma_rx_is_lockedtoref
h067;
—
pcs8g_rx_status
h081;
31-6
rx_phase_comp_fifo_error
h081;
0
rx_bitslipboundaryselectout
h081;
5-1
pcs8g_tx_status
h082;
31-1
tx_phase_comp_fifo_error
h082;
0
pcs8g_tx_control
h083;
31-6
tx_invpolarity
h083;
0
tx_bitslipboundaryselect
h083;
5-1
pcs8g_rx_control
h084;
31-1
rx_invpolarity
h084;
0
The following is an example of using the signals in Table 5 for the custom PHY IP with
channel 0:
1. Read the pll_is_locked state for all channels (Figure 5):
a. Set phy_mgmt_address = 9'h022;
b. Send a read pulse
c. Read the phy_mgmt_readdata switches to 32'h00000001;
Result: This means channel 0 is locked to the PLL.
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Appendix: Stratix V Transceiver Design Guidelines
2. Enable serial loopback (Figure 5):
a. Set phy_mgmt_address = 9'h061;
b. Set phy_mgmt_writedata = 32'hffffffff //only 32'h00000001 is required
c. Send a write pulse
Result: The rx_parallel data (2nd from the bottom in Figure 5) starts outputting
data some time later after loopback is enabled. This delay represents the receiver
functional block delay within the PHY IP until the loopbacked data is accessible in
the FPGA fabric.
3. Read pma_is_lockedtoref and pma_is_lockedtodata (Figure 5):
a. Set phy_mgmt_address = 9'h066;
// lockedtoref
b. Send a read pulse
c. Phy_mgmt_readdata is 32'h00000001; // for channel 0
d. Set phy_mgmt_address = 9'h067;
// lockedtodata
e. Send a read pulse
f. Phy_mgmt_readdata is 32'h00000001; // for channel 0
Result: The read addresses for pma_rx_is_lockedtoref (66) and
pma_rx_is_lockedtodata (67) are both high for channel 0. These signals are not
mutually exclusive. If pma_rx_is_lockedtodata is high, the CDR is locked to data
no matter the state of pma_rx_is_lockedtoref.
Figure 5. Direct Read (PLL Locked) and Write (Serial Loopback), rx_is_lockedto (Reference and Data)
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Appendix: Stratix V Transceiver Design Guidelines
Page 65
4. Set the mask to reset the individual receivers and transmitters (Figure 6):
a. Set phy_mgmt_address = 9h041;
// Reset_Chip_Mask
b. Set phy_mgmt_writedata = 32'h00000001; // all F' to reset all
c. Send a write pulse
Result: This sets the reset chip mask to focus on only channel 0.
5. Reset the channel 0 transmitter (Figure 6):
a. Set phy_mgmt_address = 9'h042;
//reset control
b. Set phy_mgmt_writedata = 32'h00000001; // select the TX reset =bit 0
c. Send a write pulse
Result: The readdata output for this location has tx_ready in bit location 0 and the
rx_ready in bit location 1. The write pulse tx_ready bit goes low and then comes
back (data goes from 11 to 10 and back to 11). This information is delayed from the
tx_ready output transitions. This is the normal latency through the management
interface because readdata is a registered output. This is the automatic clear reset
so you do not have to write a 0 in the register.
6. Reset the channel 0 receiver (Figure 6):
a. Keep phy_mgmt_address = 9'h042;
b. Set phy_mgmt_writedata = 32'h00000002; // RX reset = bit 1
c. Send a write pulse
Result: readdata for this location has tx_ready in bit 0 and rx_ready in bit 1. After
the write pulse, rx_ready goes low and then comes back (data goes from 11 to 01
and back to 11). This information is delayed from the rx_ready output transitions.
This is the normal latency through the management interface because readdata is
a registered output. This is the automatic clear reset so you do not have to write a 0
in the register.
Figure 6. Reset Control with Automatic Clear
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Appendix: Stratix V Transceiver Design Guidelines
7. Flexible fine reset control (bypasses the reset controller) shown in Figure 7:
a. Set phy_mgmt_address = 9'h044;
// Fine Reset Control
b. Set phy_mgmt_writedata = 32'h0000000e; // 1110 to reset all resets
c. Send a write pulse
1
The tx_ready and rx_ready signals come from the automatic reset controller and can
not be used to monitor the readiness using fine_reset_control. In the next section,
writing a 0 in the reset location turns off the reset after user delay for a user flexible
reset sequence.
d. Custom delay for all reset:
Set phy_mgmt_writedata = 32'h0000000c; // 1100 releases the TX digital reset
bit
e. Send a write pulse
f. Custom delay for the RX reset:
Set phy_mgmt_writedata = 32'h00000008; // 1000 deselects RX analog reset bit
g. Send a write pulse
h. Custom delay for the RX digital reset:
Set phy_mgmt_writedata = 32'h00000000; // deselects the RX digital reset bit
Figure 7. Manual Reset Requires Clear
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December 2013 Altera Corporation
Appendix: Stratix V Transceiver Design Guidelines
Page 67
Compiling a Real Design
After you have simulated the design, work on a real Quartus II design. If you have
used Stratix IV transceivers, you may have noticed that many selections in the ALTGX
megafunction are not made in the PHY IP. The following section discusses how the
selections are moved to the Assignment Editor or .qsf.
Set the Quartus II Settings File Using the Assignment Editor and the Settings
Dialog Box
Beginning with Stratix V devices, the analog settings (the settings that cannot be
observed in digital simulation) are set using .qsf assignments applied in the
Assignment Editor or in the Settings dialog box. This approach avoids modifying the
RTL when such a setting requires an update. Specifically, you do not have to
re-synthesize the design when analog parameters change.
There are two modes of use for these .qsf assignments:
■
When a .qsf assignment is present, the assigned value is validated by the
Quartus II software. Assuming the value is valid, it is applied to a block and
becomes a configuration.
■
When a .qsf assignment does not exist, the Quartus II software computes a valid
value for the parameter. This is the default and preferred use model.
To set Termination
Table 6 shows the available setting to set termination with GXB pins.
Table 6. GXB Pin Termination Options in the Assignment Editor
QSF Variable Name
GXB_IO_PIN_TERMINATION
GXB_DEDICATED_REFCLK_PIN_TERMINATION
Default Value
100_OHMS
AC_COUPLING
Valid Values
■
150_OHMS
■
120_OHMS
■
100_OHMS
■
85_OHMS
■
EXTERNAL_RESISTOR
■
DC_COUPLING_INTERNAL_100_OHMS
■
DC_COUPLING_EXTERNAL_RESISTOR
■
AC_COUPLING
For example, setting the receiver serial data (rx_serial_data) channel to have 100
ohms termination in the Assignment Editor writes the following to the .qsf:
set_instance_assignment -name GXB_IO_PIN_TERMINATION 100_OHMS -to rx_serial_data
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Appendix: Stratix V Transceiver Design Guidelines
Setting the Transceiver Voltage Levels
To find the default values or settings for transceiver voltage levels in the current
project, on the Assignments menu, click Settings. In the Category list, expand
Operating Settings and Conditions and select Voltage. Use the pull-down menu to
select the voltage value you want to change in the Setting column. When the values
are selected, click Apply. The value is correctly written to the .qsf. Verify the values
you enter match the Stratix V Pin Connection Guidelines voltage levels for the
transceiver data rate or it may not compile. You can always use the voltage levels for a
higher data rate configuration.
For example, set_global_assignment -name VCCT_L_USER_VOLTAGE 1.0V is written
to the .qsf if you select 1.0 V in the Voltage page of the Setting dialog box (Figure 8).
Figure 8. Selecting 1.0 V in the Voltage Page of the Settings Dialog Box
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Setting PLL Assignments
The Quartus II software automatically picks the best internal settings and the best
location for the PLL. These settings are available in the Assignment Editor if they are
required. Selecting the PLL type as ATX PLL is the most common transceiver PLL
option. The default PLL type is CMU PLL. Table 7 shows the .qsf names for the
different PLLs.
Table 7. PLL Assignments
.qsf Name
FPLL
CMU
PLL
ATX PLL
MERGE_TX_PLL_DRIVEN_BY_REGISTERS_WITH_SAME_CLEAR
v
v
v
PLL_CHANNEL_SPACING
v
—
—
PLL_COMPENSATION
v
—
—
PLL_COMPENSATION_MODE
v
v
v
PLL_OUTPUT_CLOCK_FREQUENCY
v
v
v
PLL_PFD_CLOCK_FREQUENCY
v
v
v
PLL_VCO_CLOCK_FREQUENCY
v
v
v
MATCH_PLL_COMPENSATION_CLOCK
v
—
—
PLL_TYPE
v
v
v
Setting the PLL TYPE to ATX PLL
In the last example directory, an auto generated file called
custom_phy_assignments.qip has a comment showing the PLL type assignment
required for each PLL in the .qsf:
#set_instance_assignment -name PLL_TYPE ATX -to
"<top_level|...|<my_name>:<my_name>_inst|sv_xcvr_generic_top:xcvr_custom_phy|sv_xcvr_g
eneric:transceiver_core|pll[*].tx_pll"
You can use the Assignment Editor to automatically write the comment in the .qsf.
Search for the *.tx_pll in the Node Finder for the list of tx_plls signals used in this
design.
In the previous example, when using the Node Finder for design entry and searching
for *.tx_pll in the search field, the single TX PLL location was as follows:
CustomPHY:CustomPHY_Inst|altera_xcvr_custom_phy:customphy_inst|sv_xcvr_custom_phy:S5|s
v_xcvr_generic_top:xcvr|sv_xcvr_generic:transceiver_core|pll[0].tx_pll
To automatically write the ATX PLL assignment for the PLL location, use the Node
Finder and Assignment Editor.
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First, locate the tx_plls in the Node Finder as shown in Figure 9.
Figure 9. Using the Node Finder to Locate the tx_plls
Use the Assignment Editor to assign the name and value to the node, as shown in
Figure 10.
Figure 10. Using the Assignment Editor to Assign a tx_pll as a ATX PLL
This design is only 1250 Mbps (the default data rate for this configuration), so the ATX
PLL cannot be used. The design may fail when it is compiled because the settings for
the ATX PLL could not attain the VCO rate of 625 Mbps. The ATX PLL has data rate
restrictions and the valid choices should be reviewed in the DC and Switching
Characteristics for Stratix V Devices chapter.
Moving the Test Bench into the Design
In the simulation section, the master for the transceiver block Avalon-MM control and
status registers was assigned through the test bench. In a real design, this function is
driven by a microprocessor but in a simple design, this function is driven by a state
machine.
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Appendix: Stratix V Transceiver Design Guidelines
Page 71
For the state machine, there should be a reset state 0, and a check for the correct status
in each state before moving to the next state (for example, refer to Figure 11).
Figure 11. Example of Moving Through Each State in a State Machine
After Power Up
State 0
Proper Reset Sequence
Go to State 1
State 1
Check for the pll_is_lockedto Reference
If Yes, Go to State 2
or
Stay in State 1 Until the
Maximum Time Limit, Then
Go to State 0
State 2
Turn on Loopback Mode (or Enable Other Device)
Check for pll_is_lockedtodata
If Yes, Go to State 3
or
Stay in State 2 Until the
Maximum Time Limit, Then
Go to State 0
State 3
Send Align Pattern
Check the rx_synchstatus Signal for Alignment
If Yes, Go to State 4
or
Stay in State 3 Until the
Maximum Time Limit, Then
Go to State 0
State 4
Send Data
Check Status
If Correct, Stay in State 4
or
Go to State 3
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Appendix: Stratix V Transceiver Design Guidelines
The state machine can have many more status checks and can be smarter on what it
does if the desired outcome is not achieved to closely match the system or protocol
requirements.
Stratix V Device Design Guidelines
December 2013 Altera Corporation
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