User guide

Chapter 7: Custom PHY IP Core 7–5
Parameter Settings
December 2010 Altera Corporation Altera Transceiver PHY IP Core User Guide
Word Alignment
The word aligner restores word boundaries of received data based on a predefined
alignment pattern. This pattern can be 7, 8, 10, 16, 20, or 32 bits long. The word
alignment module searches for a programmed pattern to identify the correct
boundary for the incoming stream. Table 7–4 lists the settings available on the Word
Aligner tab.
Table 7–4. Word Aligner Options
Name Value Description
Word alignment mode
Manual
You can select 1 of the following 3 modes:
■ Manual—In this mode you enable the word alignment function by
asserting
rx_enapatternalign using the Avalon-MM interface.
Word aligner starts searching for the alignment pattern as soon as
this control signal is asserted.
Bit slipping
■ Bit Slip Mode—You can use bit slip mode to shift the word
boundary using the Avalon-MM interface. For every rising edge of
the
rx_bitslip signal, the word boundary is shifted by 1 bit.
Each bit slip removes the earliest received bit from the received
data.
Automatic
synchronization
state machine
■ Automatic Synchronization State Machine Mode—In this mode,
word alignment is controlled by a programmable state machine.
This mode can only be used with 8B/10B encoding. The data width
at the word aligner can be 10 or 20 bits. You can specify the
following parameters:
■ Number of consecutive valid words before sync state is
reached: Specifies the number of consecutive valid words
needed to reduce the built up error count by 1. Valid values are
0–255.
■ Number of bad data words before loss of sync state: Specifies
the number of bad data words required for alignment state
machine to enter loss of sync state. Valid values are 0–255.
■ Number of valid patterns before sync state is reached:
Specifies the number of consecutive patterns required to
achieve synchronization.Valid values are 0–255.
■ Word alignment pattern length: Allows you to specify a 7- or
10-bit pattern for use in the word alignment state machine.
■ Word alignment pattern: Allows you to specify a word
alignment pattern.
Enable run length violation
checking
On/Off
If you turn this option on, you can specify the run length which is the
maximum legal number of contiguous 0s or 1s.
Run length 40–640 Specifies the threshold for a run-length violation.