Virtex-5 RocketIO GTP Transceiver User Guide
195
UG196 (v1.3) May 25, 2007
R
Chapter 9
Loopback
Overview
Loopback modes are specialized configurations of the transceiver datapath where the
traffic stream is folded back to the source. Typically, a specific traffic pattern is transmitted
and then compared to check for errors.
illustrates a loopback test configuration
with four different loopback modes.
Loopback test modes fall into two broad categories:
•
Near-end loopback modes loop transmit data back in the transceiver closest to the
traffic generator.
•
Far-end loopback modes loop received data back in the transceiver at the far end of
the link.
Loopback testing can be used either during development or in deployed equipment for
fault isolation. The traffic patterns used can be either application traffic patterns, or
specialized Pseudo Random Bit Streams (PRBS). Each GTP transceiver has a built-in PRBS
generator and checker.
Each channel of the GTP_DUAL tile features several loopback modes to facilitate testing:
•
Near-End PCS Loopback (path 1 in
)
•
Near-End PMA Loopback (path 2 in
•
Far-End PMA Loopback (path 3 in
•
Far-End PCS Loopback (path 4 in
)
Figure 9-1:
Loopback Testing Overview
Near-End GTP
Link Near-End Test Structures
Link Far-End Test Structures
Test Logic
UG196_c9_01_011507
RX-PMA
RX-PCS
TX-PMA
TX-PCS
Far-End GTP
RX-PMA
RX-PCS
TX-PMA
TX-PCS
Traffic
Checker
Traffic
Generator
1
4
3
2
Содержание Virtex-5 RocketIO GTP
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