Altera Corporation
5–1
July 2005
5. High-Speed Differential I/O
Interfaces in Stratix Devices
Introduction
To achieve high data transfer rates, Stratix devices support True-
LVDSTM differential I/O interfaces which have dedicated
serializer/deserializer (SERDES) circuitry for each differential I/O pair.
Stratix SERDES circuitry transmits and receives up to 840 megabits per
second (Mbps) per channel. The differential I/O interfaces in Stratix
devices support many high-speed I/O standards, such as LVDS,
LVPECL, PCML, and HyperTransportTM technology. Stratix device high-
speed modules are designed to provide solutions for many leading
protocols such as SPI-4 Phase 2, SFI-4, 10G Ethernet XSBI, RapidIO,
HyperTransport technology, and UTOPIA-4.
The SERDES transmitter is designed to serialize 4-, 7-, 8-, or 10-bit wide
words and transmit them across either a cable or printed circuit board
(PCB). The SERDES receiver takes the serialized data and reconstructs the
bits into a 4-, 7-, 8-, or 10-bit-wide parallel word. The SERDES contains the
necessary high-frequency circuitry, multiplexer, demultiplexer, clock,
and data manipulation circuitry. You can use double data rate I/O
(DDRIO) circuitry to transmit or receive differential data in by-one (
×1)
or by-two (
×2) modes.
1
Contact Altera Applications for more information on other B
values that the Stratix devices support and using
×7-mode in the
Quartus II software. Stratix devices currently only support
B = 1 and B = 7 in
×7 mode.
This chapter describes the high-speed differential I/O capabilities of
Stratix programmable logic devices (PLDs) and provides guidelines for
their optimal use. You should use this document in conjunction with the
Stratix Device Family Data Sheet section of the Stratix Device Handbook,
Volume 1. Consideration of the critical issues of controlled impedance of
traces and connectors, differential routing, termination techniques, and
DC balance gets the best performance from the device. Therefore, an
elementary knowledge of high-speed clock-forwarding techniques is also
helpful.
Stratix I/O Banks
Stratix devices contain eight I/O banks, as shown in
Figure 5–1. The two
I/O banks on each side contain circuitry to support high-speed LVDS,
LVPECL, PCML, HSTL Class I and II, SSTL-2 Class I and II, and
HyperTransport inputs and outputs.
S52005-3.2