Xilinx 7 Series User Manual
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7 Series FPGAs GTP Transceivers User Guide www.xilinx.com 205UG482 (v1.9) December 19, 2016RX Channel BondingSetting the Maximum SkewWhen the master receives a channel bonding sequence, it does not trigger channel bondingimmediately. Several more bytes must arrive if the slaves have more latency. This wait timeeffectively becomes the maximum skew that the RX elastic buffer can handle. If the skew is greaterthan this wait time, the slaves might not receive the sequence by the time the master triggers channelbonding.Figure 4-52 shows two FIFOs, one for the master and one for the slave. If the slave is behind themaster, the master must wait several cycles before triggering channel bonding, otherwise the slowslave does not have the channel bonding sequence in its buffer.CHAN_BOND_MAX_SKEW is used to set the maximum skew allowed for channel bondingsequences 1 and 2. The maximum skew range is 1 to 14. This range must always be less thanX-Ref Target - Figure 4-51Figure 4-51: Channel Bonding Sequence MappingCHAN_BOND_SEQ_x_4 CHAN_BOND_SEQ_x_3 CHAN_BOND_SEQ_x_2 CHAN_BOND_SEQ_x_1CHAN_BOND_SEQ_x_ENABLE 4 3 2 1 UG482_c4_33_111011X-Ref Target - Figure 4-52Figure 4-52: Channel Bonding Example (CHAN_BOND_MAX_SKEW = 2 andMaster RXCHANBONDLEVEL[2:0] = 1)D1D2D3D4D5D6D7SEQ1D1D2D3D4D5D6D7 D0D4D5D6D7SEQ1D8D9D10D4D5D6D7SEQ1D8D9 D3D5D6D7SEQ1D8D9D10D11D5D6D7SEQ1D8D9D10 D4SlaveElasticBufferMasterElasticBufferSlave’s New ElasticBuffer Read PointerMaster receives CB SequenceThe master waits CHAN_BOND_MAX_SKEWcycles before triggering channel bonding, givingthe slave time to receive the sequence. Themessage to perform channel bonding is sentusing the RXCHBONDO port.The RXCHANBONDLEVEL setting of the masterdetermines how many cycles later the bondingoperation is executed. At this time, the slave’selastic buffer pointers are moved so that theoutput is deskewed.SlaveElasticBufferMasterElasticBufferSlaveElasticBufferMasterElasticBufferUG482_c4_34_111011Send Feedback |
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