Chbonddone; Chbondi, Chbondo; Rxclkcorcnt, Rxlossofsync; Troubleshooting - Xilinx RocketIO User Manual

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Channel Bonding (Channel Alignment)

CHBONDDONE

This port indicates when a channel alignment has occurred in the MGT. When it is
asserted, RXDATA is valid after RXCLKCORCNT goes to a 101.
CHBONDI,
CHBONDO
These two 4-bit ports are used by the Master MGT to control its clock correction and
channel bonding, as well as those of any Slaves bonded to it. CHBONDO of the Master is
connected to CHBONDI of a SLAVE_1_HOP. The signal is then daisy-chained from
SLAVE_1_HOP CHBONDO to a SLAVE_2_HOPS CHBONDI. See
Figure 4-2, page
correlate to the value of the RXCLKCORCNT port. These four bits allow the Master to
control when the Slaves perform clock correction. This keeps channels from going out of
sync if, for instance, one Slave repeated a CCS while another skipped.
RXCLKCORCNT,
RXLOSSOFSYNC
These signals are mainly used for clock correction. However, they can convey some
information relevant to channel bonding as well. Refer to
"RXLOSSOFSYNC," page

Troubleshooting

Factors that influence channel bonding include:
•
•
There are several possibilities that could cause unsuccessful channel bonding:
•
•
•
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Note:
The Slave's RXCLKCORCNT will go to 101 regardless of whether the channel bonding
was successful or not. To determine if channel bonding was successful, check both this signal
and RXCLKCORCNT.
122, and Table 2-18, page
77.
Skew between Master and Slave CBS arrival time, both Master-lags-Slave and Slave-lags-
Master cases. The larger the separation, the larger CHAN_BOND_WAIT needs to be.
Arrival time between consecutive CBSs. The smaller the separation is between
consecutive CBSs, the smaller CHAN_BOND_WAIT needs to be set to ensure that the
Master aligns to the intended sequence instead of the one after or the one before.
Slave's CBS lagging the master by too much. Essentially, the Slave does not see a CBS
when CHBONDO is asserted.
Master CBS lags the slave by too much. In this case, the slave's CBS sequence has
exceeded CHAN_BOND_LIMIT and has expired.
CBS sequences appear more frequently than CHAN_BOND_LIMIT allows, causing the
Slave to align to a CBS before or after the expected one.
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Figure 4-1
80, for examples. The three least significant bits
"RXCLKCORCNT"
R
and
and
83