Altera Corporation
2–115
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Figure 2–93. Double-Width Byte Ordering With Two Pad Byte Inserts
Figure 2–94
shows the byte ordering block in single-width mode two-lane
configuration. In
Figure 2–94
, the alignment pattern “A” is in the MSByte
position (lane 1). The byte ordering block inserts a pad character to force
the alignment character to the LSByte position (lane 0). If the alignment
pattern already exists in lane 0, the byte ordering process completes
without any ordering done because it is unnecessary. After the ordering
process is complete, the
rx_byteorderalignstatus
signal asserts
and stays high until
rx_digitalreset
,
rx_analogreset
, or
gxb_powerdown
is asserted to reset the byte ordering block.
Figure 2–94. Single-Width Byte Ordering With One Pad Insert
PLD-Controlled Byte Ordering
Unlike word alignment based byte ordering, PLD-controlled byte
ordering provides control to the user logic to restore correct byte order at
the receiver. When enabled, an
rx_enabyteord
port is available at the
PLD interface. A rising edge on the
rx_enabyteord
port triggers the
byte ordering block. The byte ordering block looks for the
user-programmed byte ordering pattern in the data stream from the byte
deserializer. When the byte reordering block finds the byte ordering
pattern, it inserts the user-programmed pad byte in the data stream until
the byte ordering pattern can be placed in the LSByte position. When the
byte ordering pattern is placed in the LSByte position, the byte ordering
process is complete and the status signal
rx_byteorderalignstatus
is asserted (stays high). If the alignment pattern is already in the LSByte
position, the byte ordering block does not add any pad byte, considers the
byte ordering process complete, and asserts the
rx_byteorderalignstatus
signal.
PD D3
PD D2
Byte
Ordering
X
D1
X
Lane 3
Lane 2
Lane 1
Lane 0
A
D1
X
A
X
X
D3
X
D2
PD D1
D0
A
Byte
Ordering
Lane 1
Lane 0
A
D2
D0
D1