Xilinx RocketIO User Manual

Also see for RocketIO: User guide User guide User guide

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Xilinx RocketIO User Manual Manual pdf 80 page image

80 www.xilinx.com RocketIO™ Transceiver User GuideUG024 (v3.0) February 22, 2007Chapter 2: Digital Design ConsiderationsRChannel Bonding (Alignment) OperationChannel bonding is the technique of tying several serial channels together to create oneaggregate channel. Several channels are fed on the transmit side by one parallel bus andreproduced on the receive side as the identical parallel bus. The maximum number ofserial differential pairs that can be bonded is 24. For implementation guidelines, see“Implementation Tools,” page 121.Channel bonding allows those primitives that support it to send data over multiple“channels.” Among these primitives are GT_CUSTOM, GT_INFINIBAND, GT_XAUI, andGT_AURORA. To “bond” channels together, there is always one “Master.” The otherchannels can either be a SLAVE_1_HOP or SLAVE_2_HOPS. SLAVE_1_HOP is a Slave to aMaster that can also be daisy chained to a SLAVE_2_HOPS. A SLAVE_2_HOPS can only bea Slave to a SLAVE_1_HOP and its CHBONDO does not connect to another transceiver. Todesignate a transceiver as a Master or a Slave, the attribute CHAN_BOND_MODE must beset to one of three designations: Master, SLAVE_1_HOP, or SLAVE_2_HOPS. To shut offchannel bonding, set the transceiver attribute to “off.” The possible values that can be usedare shown in Table 2-18.Note: All standards that use both clock correction and channel bonding require a gap greaterthan or equal to 4 bytes between clock correction and channel bonding sequences. If a usercreates his/’her own protocol that uses clock correction and channel bonding, the user mustensure that there is at least a 4 byte gap between the sequences.The channel bonding sequence is similar in format to the clock correction sequence. Thissequence is set to the appropriate sequence for the primitives supporting channel bonding.The GT_CUSTOM is the only primitive allowing modification to the sequence. Thesesequences are comprised of one or two sequences of length up to 4 bytes each, as set byCHAN_BOND_SEQ_LEN and CHAN_BOND_SEQ_2_USE. Other control signals includethe attributes:• CHAN_BOND_WAIT• CHAN_BOND_OFFSET• CHAN_BOND_LIMIT• CHAN_BOND_ONE_SHOTTypical values for these attributes are:CHAN_BOND_WAIT = 8CHAN_BOND_OFFSET = CHAN_BOND_WAITCHAN_BOND_LIMIT = 2 x CHAN_BOND_WAITLower values are not recommended. Use higher values only if channel bonding sequencesare farther apart than 17 bytes.Table 2-18: Bonded Channel ConnectionsMode CHBONDI CHBONDOOFF NA NAMASTER NA Slave 1 CHBONDISLAVE_1_HOP Master CHBONDO Slave 2 CHBONDISLAVE_2_HOPS Slave 1 CHBONDO NAProduct Not Recommended for New Designs