Loopback - Xilinx 7 Series User Manual

Chapter 2: Shared Features
TX and RX Power Down
When the TX and RX power control signals are used in non PCI Express implementations, TXPD
and RXPD can be used independently. Also, when these interfaces are used in non PCI Express
applications, only two power states are supported, as shown in
power-down mechanism, these must be true:
•
•
•
•
Table 2-26: TX and RX Power States for Operation that are not for PCI Express
Designs

Loopback

Functional Description
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.
modes.
X-Ref Target - Figure 2-22
Link Near-End Test Structures
Test Logic
Traffic
Checker
Traffic
Generator
Loopback test modes fall into two broad categories:
•
•
64
Send Feedback
TXPD[1] and TXPD[0] are connected together.
RXPD[1] and RXPD[0] are connected together.
TXDETECTRX must be strapped Low.
TXELECIDLE must be strapped to TXPD[1] and TXPD[0].
TXPD[1:0] or
RXPD[1:0]
Normal mode. Transceiver TX or RX is active sending or receiving data.
00
Power-down mode. Transceiver TX or RX is idle.
11
Figure 2-22 illustrates a loopback test configuration with four different loopback
Near-End GTP
RX-PCS RX-PMA
1
TX-PCS TX-PMA
Figure 2-22: 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.
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Table
Description
Link Far-End Test Structures
TX-PMA
2 3
RX-PMA
7 Series FPGAs GTP Transceivers User Guide
2-26. When using this
Far-End GTP
TX-PCS
4
RX-PCS
UG482_c2_11_111111
UG482 (v1.9) December 19, 2016