Xilinx RocketIO User Manual

Also see for RocketIO: User guide User guide User guide

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Xilinx RocketIO User Manual Manual pdf 61 page image

RocketIO™ Transceiver User Guide www.xilinx.com 61UG024 (v3.0) February 22, 20078B/10B Encoding/Decoding RPorts and AttributesTXBYPASS8B10B,RX_DECODE_USEOne port and one attribute enable 8B/10B encoding/decoding in the transceiver.TXBYPASS8B10B is a byte-mapped port that is 1, 2, or 4 bits wide, depending on the datawidth of the transceiver primitive being used. These bits correlate to each byte of the datapath. To enable 8B/10B encoding in the transmitter, these bits must be set Low. In thismode, the transmit data input to the TXDATA port is non-encoded data of either 8, 16, or32 bits wide. However, if other encoding schemes are preferred, the encoder capabilitiescan be bypassed by setting all bits High. In this mode, the data input to TXDATA is either10, 20, or 40 bits wide. The extra bits are fed through the TXCHARDISPMODE andTXCHARDISPVAL buses (shown in Table 2-10).The decoder is controlled by the attribute RX_DECODE_USE. When this attribute is set toTRUE, the decoder is enabled and should coincide with TXBYPASS8B10B being set Low. Inthis mode, the received data output from the RXDATA port is decoded data, either 8, 16, or32 bits wide. However, when the attribute is set to FALSE, the decoder is disabled. In thismode, the received data is 10, 20, or 40 bits wide, and the extra bits are provided byRXCHARISK and RXRUNDISP (shown in Table 2-10).If this pair is not matched, the data is not received correctly. Figure 2-12 shows theencoding/decoding blocks of the transceiver and how the data passes through theseblocks. Table 2-10 shows the significance of 8B/10B ports that change purpose dependingon whether 8B/10B is bypassed or enabled.Figure 2-12: 8B/10B Data FlowUG024_09_020507TX+TX−RX+RX−Channel BondingandClock CorrectionTX Clock GeneratorRX Clock RecoveryREFCLKDeserializerSerializer TransmitBufferTransmitterReceiverTransceiver Module32/16/8 bits32/16/8 bits50 – 156.3 MHz8B/10BEncodeElasticBufferReceiveBuffer20X MultiplierPhysical Coding Sublayer Physical Media AttachmentMindspeed IPCRCCRCFIFO8B/10BDecodeRXDATALoop-backLoop-back (parallel)TXDATAComma DetectProduct Not Recommended for New Designs