Chapter 9: Loopback; Overview - Xilinx Virtex-5 RocketIO GTP User Manual

R
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.
with four different loopback modes.
Link Near-End Test Structures
Test Logic
Traffic
Checker
Traffic
Generator
Loopback test modes fall into two broad categories:
•
•
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:
•
•
•
•
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Near-End GTP
RX-PMA
RX-PCS
1
TX-PCS TX-PMA
Figure 9-1: Loopback Testing Overview
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.
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
www.xilinx.com
Figure 9-1 illustrates a loopback test configuration
Link Far-End Test Structures
TX-PMA
2 3
RX-PMA
Figure 9-1)
Figure 9-1)
Figure 9-1)
Figure 9-1)
Chapter 9
Far-End GTP
TX-PCS
4
RX-PCS
UG196_c9_01_011507
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