Diagnostic Signals; Loopback; Table 5-4: Loopback Modes - Xilinx RocketIO User Manual

R

Diagnostic Signals

Often a diagnostic check is needed upon power-up. RocketIO transceivers have several
inputs and outputs to run these checks.

LOOPBACK

LOOPBACK allows the user to send the data that is being transmitted directly to the
receiver of the transceiver.

Table 5-4: LOOPBACK Modes

102
Input
Mode
Value
Normal Mode
00
External Serial Mode
01
Internal Parallel Mode For testing of interfacing logic, the Internal Parallel
10
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Chapter 5: Simulation and Implementation
Table 5-4 shows the three modes for loopback.
The normal mode is selected during normal operation.
The transmitted data is sent out the differential
transmit ports (TXN, TXP) and are sent to another
transceiver without being sent to its own receiver logic.
During normal operation, the LOOPBACK should be
set to "00".
The external serial mode is used to check that the entire
transceiver is working properly. This includes testing of
the 8B/10B encoding/decoding. This emulates what
another transceiver would receive as data from this
specific transceiver design.
Mode allows the use of linking the transmit and receive
interface logic without having to go to another
transceiver in the cases of 8B/10B bypassed or to
reduce data latency from TXDATA to RXDATA.
Description
UG024 (v1.5) October 16, 2002
RocketIO™ Transceiver User Guide