Xilinx RocketIO User Manual
Also see for RocketIO: User guideUser guideUser guide
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Contents
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62 www.xilinx.com RocketIO™ Transceiver User GuideUG024 (v3.0) February 22, 2007Chapter 2: Digital Design ConsiderationsRTXCHARDISPVAL,TXCHARDISPMODETXCHARDISPVAL and TXCHARDISPMODE are dual-purpose ports for the transmitterdepending upon whether 8B/10B encoding is enabled. Table 2-10 shows this dualfunctionality. When encoding is enabled, these ports function as byte-mapped controlports controlling the running disparity of the transmitted serial data.In the encoding configuration, the disparity of the serial transmission can be controlledwith the TXCHARDISPVAL and TXCHARDISPMODE ports. When TXCHARDISPMODEis set High, the running disparity is set before encoding the specific byte.TXCHARDISPVAL determines if the disparity is negative (set Low) or positive (set High).Table 2-11 illustrates this.Table 2-10: 8B/10B Bypassed Signal SignificanceFunctionTXBYPASS8B10B 0 8B/10B encoding is enabled (not bypassed). 1, 2, or 4 bits, mapped to number ofbytes of data path width.1 8B/10B encoding bypassed (disabled). 1, 2, or 4 bits, mapped to number of bytesof data path width.Function, 8B/10B Enabled Function, 8B/10B BypassedTXCHARDISPMODE,TXCHARDISPVAL 00 Maintain running disparity normally Part of 10-bit encoded byte(see Figure 2-13):TXCHARDISPMODE[0](or: [1] / [2] / [3])TXCHARDISPVAL[0](or: [1] / [2] / [3])TXDATA[7:0](or: [15:8] / [23:16] / [31:24])01 Invert the normally generated runningdisparity before encoding this byte.10 Set negative running disparity beforeencoding this byte.11 Set positive running disparity beforeencoding this byte.RXCHARISK Received byte is a K-character Part of 10-bit encoded byte(see Figure 2-14):RXCHARISK[0](or: [1] / [2] / [3])RXRUNDISP[0](or: [1] / [2] / [3])RXDATA[7:0](or: [15:8] / [23:16] / [31:24])RXRUNDISP0 Indicates running disparity isNEGATIVE1 Indicates running disparity isPOSITIVERXDISPERR Disparity error occurred on currentbyteUnusedTXCHARISK Transmitted byte is a K-character UnusedRXCHARISCOMMA Received byte is a comma UnusedProduct Not Recommended for New Designs |
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