Related Information
Altera Transceiver PHY IP Core User Guide
PIPE Reverse Parallel Loopback
This section describes PIPE Reverse Parallel Loopback debugging option using parallel data through the
rate match FIFO, transmitter serializer, and
tx_serial_data
port path.
PIPE reverse parallel loopback is only available in the PCIe
®
configuration for Gen1 and Gen2 data rates.
Figure 2 shows the received serial data passing through the receiver CDR, deserializer, word aligner, and
rate match FIFO buffer. The parallel data from the rate match FIFO is then looped back to the transmitter
serializer and transmitted out through the
tx_serial_data
port. The received data is also available to
the FPGA fabric through the
rx_parallel_data
signal.
PIPE reverse parallel loopback is compliant with the PCIe 2.0 specification. To enable this loopback
configuration, assert the
tx_detectrx_loopback
signal.
PIPE reverse parallel loopback is the only loopback option supported in the PCIe configuration.
Note:
Figure 6-3: PIPE Reverse Parallel Loopback Configuration Datapath
Transmitter PCS
Note: Grayed-out blocks are not active when the PIPE reverse parallel loopback is enabled.
Transmitter PMA
Receiver PMA
Receiver PCS
FPGA
Fabric
PIPE
Interface
Byte
Ordering
RX
Phase
Compensation
FIFO
rx_parallel_data
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 Parallel Loopback Path
PCI
Express
Hard
IP
Reverse Serial Loopback
You can use the reverse serial loopback option to debug with data through the
rx_serial_data port
,
receiver CDR, and
tx_serial_data
port path.
You can enable reverse serial loopback through the reconfiguration controller.
For further details, refer to the Altera Transceiver PHY IP Core User Guide.
Note:
In reverse serial loopback, the data is received through the
rx_serial_data
port, re-timed through the
receiver CDR, and sent to the
tx_serial_data
port. The received data is also available to the FPGA
logic. No dynamic pin control is available to select or deselect reverse serial loopback.
The transmitter buffer is the only active block in the transmitter channel. You can change the V
OD
and the
pre-emphasis first post tap values on the transmitter buffer through the dynamic reconfiguration controller.
Altera Corporation
Transceiver Loopback Support
6-3
PIPE Reverse Parallel Loopback
CV-53006
2013.05.06