1–72 Chapter 1: Cyclone IV Transceivers Architecture
Transceiver Functional Modes
Cyclone IV Device Handbook, February 2015 Altera Corporation
Volume 2
■ Channel alignment is acquired if three additional aligned ||A|| columns are
observed at the output of the deskew FIFOs of the four channels after alignment of
the first ||A|| column.
■ Channel alignment is indicated by the assertion of
rx_channelaligned
signal.
■ After acquiring channel alignment, if four misaligned ||A|| columns are seen at
the output of the deskew FIFOs in all four channels with no aligned ||A||
columns in between, the
rx_channelaligned
signal is deasserted, indicating loss of
channel alignment.
Figure 1–65 shows lane skew at the receiver input and how the deskew FIFO uses the
/A/ code group to align the channels.
Lane Synchronization
In XAUI mode, the word aligner is configured in automatic synchronization state
machine mode that is compliant to the PCS synchronization state diagram specified in
clause 48 of the IEEE P802.3ae specification. Table 1–23 lists the synchronization state
machine parameters that implements the lane synchronization in XAUI mode.
Figure 1–65. Deskew FIFO–Lane Skew at the Receiver Input
Lane 0
K
KK KK
K K
KK KKK K
KK KKK K
R
K
R
K
R
K K
R
K
R
R RR RR
RRR RR
RRR RR
A
A
A
A
Lane 1
Lane 2
Lane 3
Lane 0
K
KK KK
K K
KK KKK K
KK KKK K
RK RK R K K RK R
R RR RR
RRR RR
RRR RR
A
A
A
A
Lane 1
Lanes skew at
receiver input
Lanes are deskewed by lining
up the “Align”/A/ code groups
/A/ column
Lane 2
Lane 3
Table 1–23. Synchronization State Machine Parameters
(1)
Parameter Value
Number of valid synchronization (/K28.5/) code groups received to achieve
synchronization
4
Number of erroneous code groups received to lose synchronization 4
Number of continuous good code groups received to reduce the error count by
one
4
Note to Table 1–23:
(1) The word aligner supports 7-bit and 10-bit pattern lengths in XAUI mode.
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