Altera Stratix GX Transceiver - Manual (Page 113)

Altera Corporation 5–1
January 2005
5. XAUI Mode
Introduction The 10 Gigabit Attachment Unit Interface (XAUI) is an optional,
self-managed interface that can be inserted between the reconciliation
sublayer and the PHY layer to transparently extend the physical reach of
the 10 Gigabit Media Independent Interface (XGMII).
XAUI addresses several physical limitations of the XGMII. XGMII
signaling is based on the HSTL class 1 single-ended I/O standard, which
has an electrical distance limitation of approximately 7 cm. Because XAUI
uses low voltage differential signaling method, the electrical limitation is
increased to approximately 50 cm. Another advantage of XAUI is
simplification of backplane and board trace routing. XGMII is composed
of 32 transmit channels, 32 receive channels, 1 transmit clock, 1 receive
clock, 4 transmitter control characters, and 4 receive control characters for
a 74-pin wide interface in total. XAUI, on the other hand, only consists of
4 differential transmitter channels and 4 differential receiver channels for
a 16-pin wide interface in total. This reduction in pin count significantly
simplifies the routing process in the layout design.
Figure 5–1 shows the
relationships between the XGMII and XAUI layers.
Stratix ® GX devices offer the following XAUI features:
■ Serial data rate range from 500 Mbps to 3.1875 Gbps
■ Input reference clock range from 25 to 637.5 MHz
■ Parallel interface width of 16 bits
■ 8B/10B encoder and decoder
■ Word aligner supports 10-bit code-group
■ Channel deskew
■ Rate compensation or elastic buffer
■ XGMII-to -PCS code conversion on transmit
■ PCS-to -XGMII code conversion on receive
■ Byte deserializer