Virtex-5 RocketIO GTP Transceiver User Guide www.xilinx.com 109
UG196 (v1.3) May 25, 2007
TX PRBS Generator
R
TX PRBS Generator
Overview
Pseudo-random bit sequences (PRBS) are commonly used to test the signal integrity of
high-speed links. These sequences appear random but have specific properties that can be
used to measure the quality of a link.
The GTP PRBS block can generate several industry-standard PRBS patterns. Table 6-11 lists
the available PRBS patterns and their typical use.
Ports and Attributes
Table 6-12 defines the TX PRBS generator ports.
There are no attributes in this section.
Table 6-11: Pseudo-Random Bit Sequences
Name Polynomial
Length of
Sequence (bits)
Consecutive
Zeros
Typical Use
PRBS-7
1+X
6
+X
7
(inverted)
2
7
–1 7
Used to test channels with 8B/10B.
PRBS-23
1+X
18
+X
23
(inverted)
2
23
–1 23
ITU-T Recommendation O.150, Section 5.6. One of the
recommended test patterns in the SONET specification.
PRBS-31
1+X
28
+X
31
(inverted)
2
31
–1 31
ITU-T Recommendation O.150, Section 5.8. A
recommended PRBS test pattern for 10 Gigabit
Ethernet. See IEEE 802.3ae-2002.
Table 6-12: TX PRBS Generator Ports
Port Dir
Clock
Domain
Description
TXENPRBSTST0[1:0]
TXENPRBSTST1[1:0]
In
Transmitter test pattern generation control. A pseudo-random bit sequence
(PRBS) is generated by enabling the test pattern generation circuit.
INTDATAWIDTH must also be 1 (10-bit internal data width mode) when
the PRBS generator is enabled.
00: Test pattern generation off (standard operation mode)
01: Enable 2
7
– 1 PRBS generation
10: Enable 2
23
– 1 PRBS generation
11: Enable 2
31
– 1 PRBS generation
Because PRBS patterns are deterministic, the receiver can check the received
data against a sequence of its own PRBS generator.
INTDATAWIDTH In Async
Specifies the width of the internal datapath for the entire GTP_DUAL. The
PRBS Generator will only work when INTDATAWIDTH = 1 (10-bit internal
datapath)
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