User guide

Figure 2-77: Rate Match FIFO Empty
The rate match FIFO automatically inserts /K30.7/ (9'h1FE) after the data byte that causes the FIFO to
become empty and drives pipe_rx_status[2:0] = 3'b110 synchronous to the inserted /K30.7/ (9'h1FE).
The figure below shows rate match FIFO empty condition in PIPE mode. The rate match FIFO becomes
empty after reading out data byte D3.
D1 D2 D3 D4 D5 D6
D1 D2 D3 /K.30.7/ D4
D5
tx_parallel_data
rx_parallel_data
pipe_rx_status[2:0] xxx xxx xxx 3’b110 xxx
xxx
PIPE 0 ppm
The PIPE mode also has a "0 ppm" configuration option that can be used in synchronous systems. The
Rate Match FIFO Block is not expected to do any clock compensation in this configuration, but latency
will be minimized.
PCIe Reverse Parallel Loopback
PCIe reverse parallel loopback is only available in a PCIe functional configuration for Gen1, Gen2, and
Gen3 data rates. The received serial data passes through the receiver CDR, deserializer, word aligner, and
rate matching FIFO buffer. The data is then looped back to the transmitter serializer and transmitted out
through the transmitter buffer. The received data is also available to the FPGA fabric through the
rx_parallel_data port. This loopback mode is based on PCIe specification 2.0. Arria 10 devices provide
an input signal pipe_tx_detectrx_loopback to enable this loopback mode.
Note:
This is the only loopback option supported in PIPE configurations.
Figure 2-78: PCIe Reverse Parallel Loopback Mode Datapath
PCI Express Hard IP
PIPE Interface
RX
FIFO
Byte
Deserializer
8B/10B Decoder
Rate Match FIFO
Receiver PMA
Word Aligner
Deserializer
CDR
Receiver Standard PCS
Transmitter Standard PCS
Transmitter PMA
Serializer
tx_serial_data rx_serial_data
FPGA
Fabric
TX TX
FIFOFIFO
Byte SerializerByte Serializer
8B/10B Encoder8B/10B Encoder
PRBS
Generator
TX Bit Slip
PRBS
Reverse Parallel
Loopback Path
Verifier
Related Information
Arria 10 Standard PCS Architecture on page 5-37
2-234
PCIe Reverse Parallel Loopback
UG-01143
2015.05.11
Altera Corporation
Implementing Protocols in Arria 10 Transceivers
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