Setting Channel Bonding Sequences; Setting The Maximum Skew - Xilinx Virtex-6 FPGA User Manual

Chapter 4: Receiver

Setting Channel Bonding Sequences

The channel bonding sequence is programmed in the same way as the clock correction
sequence. CHAN_BOND_SEQ_LEN sets the length of the sequence, and
CHAN_BOND_SEQ_1_* sets the values of the sequence. If CHAN_BOND_SEQ_2_USE is
TRUE, CHAN_BOND_SEQ_2_* sets the values for the alternate second sequence.
The number of active bits in each subsequence depends on RX_DATA_WIDTH and
RX_DECODE_SEQ_MATCH (see
the subsequence bits are mapped.
X-Ref Target - Figure 4-42
As with clock correction sequences, channel bonding sequences can have don't care
subsequences. CHAN_BOND_SEQ_1_ENABLE and CHAN_BOND_SEQ_2_ENABLE set
these bytes.
bonding subsequences.
X-Ref Target - Figure 4-43

Setting the Maximum Skew

When the master receives a channel bonding sequence, it does not trigger channel bonding
immediately. Several more bytes must arrive in case the slaves have more latency. This
wait time effectively becomes the maximum skew that the RX elastic buffer can handle. If
the skew is greater than this wait time, the slaves might not receive the sequence by the
time the master triggers channel bonding (see
Figure 4-44
behind the master, the master must wait several cycles before triggering channel bonding,
otherwise the slow slave does not have the channel bonding sequence in its buffer.
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CHAN BOND_SEQ_x_y
Figure 4-42: Channel Bonding Sequence Settings
Figure 4-43 shows the mapping of the enable attributes for the channel
CHAN_BOND_SEQ_x_4 CHAN_BOND_SEQ_x_3
CHAN_BOND_SEQ_x_ENABLE
Figure 4-43: Channel Bonding Sequence Mapping
shows two FIFOs, one for the master and one for the slave. If the slave is
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RX Clock Correction, page
9 8
8-Bit Channel Bonding Sequence
1 = Sequence is a K Character
0 = Sequence is Regular Character
1 = Sequence Uses Inverted Disparity
0 = Sequence Uses Regular Disparity
CHAN_BOND_SEQ_x_2
4 3 2 1
Figure 4-44).
Virtex-6 FPGA GTX Transceivers User Guide
240). Figure 4-42 shows how
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CHAN_BOND_SEQ_x_1
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UG366 (v2.5) January 17, 2011