2–206
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Loopback Modes
Use the
rx_seriallpbken
port to dynamically enable serial loopback
on a channel by channel basis. When
rx_seriallpbken
is high, all
blocks that are active when the signal is low are still active. When the
serial loopback is enabled, the
tx_dataout
port is still active and drives
out the output pins.
Serial loopback is often used to check the entire path of the transceiver.
The data is retimed through different clock domains and an alignment
pattern is still necessary for the word aligner.
Figure 2–152. Stratix II GX Block in Serial Loopback Mode
PCI Express PIPE Reverse Parallel Loopback
Figure 2–153
shows the data path for the PCI Express PIPE reverse
parallel loopback. This data path is not flexible because it must be
compliant with the PCI Express PIPE specification. The data comes in
from the
rx_datain
ports. The receiver uses the CRU, deserializer, word
aligner, and rate matching FIFO buffer, loops back to the transmitter
serializer, and then goes out the transmitter
tx_dataout
ports. The data
also goes to the PLD fabric on the receiver side to the
tx_dataout
port.
The deskew FIFO buffer is not enabled in this loopback mode. This
loopback mode is optionally controlled dynamically through the
tx_detectrxloopback
port.
1
This is the only loopback allowed in the PIPE mode.
Transmitter Digital Logic
Receiver Digital Logic
Analog Receiver and
Transmitter Logic
FPGA
Logic
Array
BIST
Incremental
Generator
TX Phase
Compensation
FIFO
RX Phase
Compen-
sation
FIFO
Byte
Serializer
8B/10B
Encoder
Serializer
Serial
Loopback
BIST
PRBS
Verify
Clock
Recovery
Unit
Word
Aligner
Deskew
FIFO
8B/10B
Decoder
Byte
De-
serializer
Byte
Ordering
BIST
Incremental
Verify
Rate
Match
FIFO
De-
serializer
BIST
PRBS
Generator
20
Содержание Stratix II GX
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