Altera Corporation
2–191
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
the PLD logic array and translate the 16-bit data words into two 8-bit data
bytes at twice the rate. The OC-48 byte deserializer takes in two
consecutive 8-bit data bytes and translates them into a 16-bit data word to
the PLD logic array at half the rate.
OC-96 Byte Serializer and Deserializer
The OC-96 byte serializer converts 32-bit data words from the PLD logic
array and translates them into two 16-bit data bytes at twice the rate. The
OC-48 byte deserializer takes in two consecutive 16-bit data bytes and
translates them into a 32-bit data word to the PLD logic array at half the
rate.
OC-48 Byte Ordering
Because of byte deserialization, the most significant byte of a word may
appear at the
rx_dataout
port along with the least significant byte of
the next word.
In an OC-48 configuration, the byte ordering block is built into the data
path and can be leveraged to perform byte ordering. In an OC-96
configuration, the byte ordering block is unavailable and ordering must
be performed in the PLD logic array.
The byte ordering in an OC-48 configuration is automatic as explained in
“Word Alignment Based on Byte Ordering” on page 2–114
. In automatic
mode, the byte ordering block is triggered by the rising edge of the
rx_syncstatus
signal. As soon as the byte ordering block sees the
rising edge of the
rx_syncstatus
signal, it compares the least
significant byte coming out of the byte deserializer with the A2 byte of the
A1A2 alignment pattern. If the least significant byte coming out of the
byte deserializer does not match A2 byte set in the MegaWizard, the byte
ordering block inserts a pad character as seen in
Figure 2–141
. Insertion
of this pad character enables the byte ordering block to restore the correct
byte order. Note that the pad character is defaulted to the A1 byte of the
A1A2 alignment pattern.
Once the byte ordering is achieved, the
rx_byteorderalignstatus
signal remains asserted high until
rx_digitalreset
is asserted. The
byte ordering within the transceiver is a one-time event after the receiver
comes out of
rx_digitalreset
. So, if a byte ordering operation is
required, the receiver must go through an
rx_digitalreset
cycle.
Содержание Stratix II GX
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