198
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Chapter 9:
Loopback
R
•
Turn the RX linear equalizer on by setting the active Low RXENEQB(0/1) signal equal
to
0
.
•
Set RXEQMIX(0/1)[1:0] to
11
.
•
Change PMA_COM_CFG[44:37] from the default value automatically set by the
RocketIO GTP Transceiver Wizard to
10101010
. This setting for
PMA_COM_CFG[44:37] must only be used for loopback. With normal data,
performance will be affected.
The attribute PMA_COM_CFG[44:37] can be changed either statically by specifying the
value in the UCF file or dynamically by changing the content of the DRP address 26[6:3] to
1111
. When switching from loopback mode to normal operation, the default value that is
set automatically by the RocketIO GTP Transceiver Wizard must be restored.
Far-End PMA Loopback
This mode uses the Near-End data source for generating and checking test data. The
loopback occurs after passing the serial-to-parallel converter of the PMA. This mode tests
the complete PMA section including the serial-to-parallel and parallel-to-serial
conversion. Almost the entire PCS section is bypassed because the RX serial inputs are
looped back to the TX serial outputs.
Marginal Conditions and Limitations
When the Far-End PMA loopback mode (
100
) is used, disregarding
PLL_RXDIVSEL_OUT, both PLL_TXDIVSEL_COMM_OUT and PLL_TXDIVSEL_OUT
must be set to
1
. Refer to
for details about the TX divider
settings.
In Far-End PMA loopback mode the TX buffer is borrowed for the parallel loopback path
to compensate for possible phase differences between the TX and RX parallel clocks. For
this reason, TX_BUFFER_USE must be TRUE when using this mode. This mode can only
be used for one transceiver at a time on any given tile due to clocking restrictions.
When one channel of a GTP_DUAL is placed in the Far-End PMA loopback mode, the TX
side of the other channel no longer operates reliably. Do not attempt nor expect reliable use
of the second channel while the first is in
100
loopback.
Figure 9-4:
Far-End PMA Loopback
Far-End GTP
UG196_c9_04_082906
RX-PMA
RX-PCS
TX-PMA
TX-PCS
P
a
r
a
l
l
e
l
Serial
Serial
Содержание Virtex-5 RocketIO GTP
Страница 1: ...R Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007...
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Страница 88: ...88 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Chapter 5 Tile Features R...
Страница 122: ...122 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Chapter 6 GTP Transmitter TX R...
Страница 186: ...186 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Chapter 7 GTP Receiver RX R...
Страница 200: ...200 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Chapter 9 Loopback R...
Страница 222: ...222 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Section 2 Board Level Design R...
Страница 256: ...256 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Section 3 Appendices R...
Страница 312: ...312 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Appendix E Low Latency Design R...