Xilinx RocketIO User Manual

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Xilinx RocketIO User Manual Manual pdf 81 page image

RocketIO™ Transceiver User Guide www.xilinx.com 81UG024 (v2.3.2) June 24, 2004 1-800-255-7778Channel Bonding (Channel Alignment) RTable 2-19 shows different settings for CHAN_BOND_ONE_SHOT and ENCHANSYNC inMaster and Slave applications.Ports and AttributesCHAN_BOND_MODEAn MGT can be designated as one of three types when used in a channel-bonding scheme. The typeis designated by CHAN_BOND_MODE, the three values of which are MASTER, SLAVE_1_HOP,and SLAVE_2_HOPS. (A fourth mode, OFF, is used when channel bonding is not being performed.)The Master always controls, for itself and for Slaves of either type, when channel bonding and clockcorrection will occur.Masters are always connected directly to a SLAVE_1_HOP, and indirectly to a SLAVE_2_HOPSvia daisy-chain through a SLAVE_1_HOP. This topology improves the timing characteristics of theCHBONDO and CHBONDI buses.ENCHANSYNCENCHANSYNC controls when channel bonding is enabled. Table 2-19 shows the recommendedsettings for Master and Slaves. To counter the possibility of a bit error causing a false channelbonding sequence to occur, this port is usually de-asserted once a group of channels have beensuccessfully aligned.CHAN_BOND_ONE_SHOTAs with ENCHANSYNC, many applications will require that the channels be aligned only once.CHAN_BOND_ONE_SHOT = TRUE allows the Master to initiate a channel bonding only once.This remains true even if more channel bonding sequences are received. (The channels may bealigned again if RXRESET is asserted and then deasserted, and ENCHANSYNC is deasserted andthen reasserted.)CHAN_BOND_ONE_SHOT may be set to FALSE when very few channel bonding sequencesappear in the data stream. (For Slave instantiations, this attribute should always be set to FALSE.See Table 2-19.) When the channel bonding sequence appears frequently in the data stream,however, it is recommended that this attribute be set to TRUE in order to prevent the RX buffer fromover- or underflowing.CHAN_BOND_SEQ_*_*,CHAN_BOND__SEQ_LEN,CHAN_BOND_SEQ_2_USEThe channel bonding sequence (CBS) is similar in format to the clock correction sequence. TheCBS is set to the appropriate sequence for the primitives supporting channel bonding.GT_CUSTOM is the only primitive allowing modification to the sequence. These sequences arecomprised of one or two sequences of length up to 4 bytes each, as set byCHAN_BOND_SEQ_LEN and CHAN_BOND_SEQ_2_USE.Table 2-19: Master/Slave Channel Bonding Attribute SettingsMaster SlaveCHAN_BOND_ONE_SHOT TRUE or FALSE as desired FALSEENCHANSYNC Dynamic control as desired Tie High