Reverse serial loopback is often implemented when using a bit error rate tester (BERT) on the upstream
transmitter.
Figure 6-4: Reverse Serial Loopback Datapath
Transmitter PCS
Note: Grayed-out blocks are not active when the reverse serial loopback is enabled.
Transmitter PMA
Receiver PMA
Receiver PCS
FPGA
Fabric
Byte
Ordering
RX
Phase
Compensation
FIFO
Byte
Deserializer
8B/10B
Decoder
Rate
Match
FIFO
Word
Aligner
Deserializer
CDR
TX
Phase
Compensation
FIFO
Byte
Serializer
8B/10B
Encoder
TX
Bit
Slip
Serializer
rx_serial_data
tx_serial_data
Reverse Serial
Loopback Datapath
Related Information
Altera Transceiver PHY IP Core User Guide
Reverse Serial Pre-CDR Loopback
This section describes reverse serial pre-CDR loopback debugging with a data path through the
rx_serial_data
port to the
tx_serial_data
port, and before the receiver CDR.
You can enable reverse serial pre-CDR loopback through the reconfiguration controller.
For further details, refer to the Altera Transceiver PHY IP Core User Guide.
Note:
In reverse serial pre-CDR loopback, the data received through the
rx_serial_data
port is looped back
to the
tx_serial_data
port before the receiver CDR. The received data is also available to the FPGA
logic. No dynamic pin control is available to select or deselect reverse serial pre-CDR loopback.
The transmitter buffer is the only active block in the transmitter channel. You can change the VOD on the
transmitter buffer through the dynamic reconfiguration controller. The pre-emphasis settings for the
transmitter buffer cannot be changed in this configuration.
Transceiver Loopback Support
Altera Corporation
CV-53006
Reverse Serial Pre-CDR Loopback
6-4
2013.05.06