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Chapter 7: GTP Receiver (RX)
Description
To use the built-in PRBS detector, RXENPRBSTST is set to match the PRBS pattern being
sent to the receiver. The RXENPRBSTST entry in
Only the 10-bit internal data width mode is supported, which implies that
INTDATAWIDTH must also be set to 1 when the PRBS checker is enabled.
When the PRBS detector is running, it attempts to find the selected PRBS pattern in the
incoming data. When it finds the pattern, it can detect PRBS errors by comparing the
incoming pattern with the expected pattern.
The detector counts the number of errors it sees and compares it with
PRBS_ERR_THRESHOLD. When the error count exceeds the threshold, RXPRBSERR is
asserted. Asserting PRBSCNTRESET clears RXPRBSERR. GTPRESET, RXCDRRESET, and
RXRESET also reset the count.
Configurable Comma Alignment and Detection
Overview
Serial data must be aligned to symbol boundaries before it can be used as parallel data. To
make alignment possible, transmitters send a recognizable sequence, usually called a
comma. The receiver searches for the comma in the incoming data. When it finds a comma,
it moves the comma to a byte boundary so the received parallel words match the
transmitted parallel words.
Figure 7-10
serial data with the comma is highlighted in the middle. The RX receiving unaligned bits
are on the right side.
100101100001001001101011100110011100101111100 1011011001010100100010101 010101100110
All Subsequent Data
Aligned to Correct
Figure 7-10: Conceptual View of Comma Alignment (Aligning to a 10-Bit Comma)
148
shows the alignment to a 10-bit comma. The TX parallel data is on the left. The
Stream of Serial Data
Alignment Block
Finds Comma
Byte Boundary
www.xilinx.com
Table 7-18
shows the available settings.
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
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Transmitted First
UG196_c7_10_092606
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