6–20
Chapter 6: I/O Features in the Cyclone III Device Family
I/O Banks
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For more information about the Cyclone III device family I/O interface with 3.3-, 3.0-,
or 2.5-V LVTTL/LVCMOS systems, refer to AN 447: Interfacing Cyclone III and
Cyclone IV Devices with 3.3/3.0/2.5-V LVTTL/LVCMOS I/O Systems.
High-Speed Differential Interfaces
The Cyclone III device family can send and receive data through LVDS signals. For
the LVDS transmitter and receiver, the input and output pins of the Cyclone III device
family support serialization and deserialization through internal logic.
The BLVDS extends the benefits of LVDS to multipoint applications such as in
bidirectional backplanes. The loading effect and the need to terminate the bus at both
ends for multipoint applications require BLVDS to drive out a higher current than
LVDS to produce a comparable voltage swing. All the I/O banks of the Cyclone III
device family support BLVDS for user I/O pins.
The reduced swing differential signaling (RSDS) and mini-LVDS standards are
derivatives of the LVDS standard. The RSDS and mini-LVDS I/O standards are
similar in electrical characteristics to LVDS, but have a smaller voltage swing and
therefore provide increased power benefits and reduced electromagnetic interference
(EMI).
The point-to-point differential signaling (PPDS) standard is the next generation of the
RSDS standard introduced by National Semiconductor Corporation. The Cyclone III
device family meets the National Semiconductor Corporation PPDS Interface
Specification and supports the PPDS standard for outputs only. All the I/O banks of
the Cyclone III device family support the PPDS standard for output pins only.
You can use I/O pins and internal logic to implement the LVDS I/O receiver and
transmitter in the Cyclone III device family. Cyclone III and Cyclone III LS devices do
not contain dedicated serialization or deserialization circuitry. Therefore, shift
registers, internal PLLs, and IOEs are used to perform serial-to-parallel conversions
on incoming data and parallel-to-serial conversion on outgoing data.
The LVDS standard does not require an input reference voltage, but it does require a
100- termination resistor between the two signals at the input buffer. An external
resistor network is required on the transmitter side for top and bottom I/O banks.
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For more information about the Cyclone III device family high-speed differential
interface support, refer to the High-Speed Differential Interfaces in the Cyclone III Device
Family chapter.
External Memory Interfacing
The Cyclone III device family supports I/O standards required to interface with a
broad range of external memory interfaces, such as DDR SDRAM, DDR2 SDRAM,
and QDRII SRAM.
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For more information about the Cyclone III device family external memory interface
support, refer to the External Memory Interfaces in the Cyclone III Device Family chapter.
Cyclone III Device Handbook
Volume 1
July 2012 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
