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Chapter 6: I/O Features in Cyclone IV Devices
6–23
Pad Placement and DC Guidelines
March 2016
Altera Corporation
External Memory Interfacing
Cyclone IV devices support I/O standards required to interface with a broad range of
external memory interfaces, such as DDR SDRAM, DDR2 SDRAM, and QDR II
SRAM.
f
For more information about Cyclone IV devices external memory interface support,
refer to the
External Memory Interfaces in Cyclone IV Devices
chapter
.
Pad Placement and DC Guidelines
You can use the Quartus II software to validate your pad and pin placement.
Pad Placement
Altera recommends that you create a Quartus II design, enter your device I/O
assignments and compile your design to validate your pin placement. The Quartus II
software checks your pin connections with respect to the I/O assignment and
placement rules to ensure proper device operation. These rules depend on device
density, package, I/O assignments, voltage assignments and other factors that are not
fully described in this chapter.
f
For more information about how the Quartus II software checks I/O restrictions, refer
to the
chapter in volume 2 of the
Quartus II Handbook
.
DC Guidelines
For the Quartus II software to automatically check for illegally placed pads according
to the DC guidelines, set the DC current sink or source value to
Electromigration
Current
assignment on each of the output pins that are connected to the external
resistive load.
The programmable current strength setting has an impact on the amount of DC
current that an output pin can source or sink. Determine if the current strength setting
is sufficient for the external resistive load condition on the output pin.
Clock Pins Functionality
Cyclone IV clock pins have multiple purposes, as per listed:
■
CLK
pins—Input support for single-ended and voltage-referenced standards. For
I/O standard support, refer to
■
DIFFCLK
pins—Input support for differential standards. For I/O standard support,
. When used as
DIFFCLK
pins, DC or AC coupling
can be used depending on the interface requirements and external termination is
required. For more information, refer to
“High-Speed I/O Standards Support” on
.
■
REFCLK
pins—Input support for high speed differential reference clocks used by
the transceivers in Cyclone IV GX devices. For I/O support, coupling, and
termination requirements, refer to
.
Содержание Cyclone IV
Страница 10: ...x Chapter Revision Dates Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 14: ...I 2 Section I Device Core Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 106: ...II 2 Section II I O Interfaces Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 164: ...III 2 Section III System Integration Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 274: ...vi Contents Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Страница 276: ...viii Chapter Revision Dates Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Страница 280: ...I 2 Section I Transceivers Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Страница 440: ...iv Contents Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
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