66 www.xilinx.com RocketIO™ Transceiver User Guide1-800-255-7778 UG024 (v2.3.2) June 24, 2004Chapter 2: Digital Design ConsiderationsRReceiving Vitesse Channel Bonding SequenceOn the RX side, the definition of the channel bonding sequence uses the disp_err bit to specifythe flipped disparity.10-bit literal value| disp_err| | char_is_k| | | 8-bit_byte_value| | | |CHAN_BOND_SEQ_1_1 = 0 0 1 10111100 matches K28.5+ (or K28.5-)CHAN_BOND_SEQ_1_2 = 0 1 1 10111100 matches K28.5+ (or K28.5-)CHAN_BOND_SEQ_1_3 = 0 0 1 10111100 matches K28.5- (or K28.5+)CHAN_BOND_SEQ_1_4 = 0 1 1 10111100 matches K28.5- (or K28.5+)CHAN_BOND_SEQ_LEN = 4CHAN_BOND_SEQ_2_USE = FALSE8B/10B Bypass Serial OutputWhen 8B/10B encoding is bypassed, the TXCHARDISPVAL and TXCHARDISPMODE bitsbecome bits “b” and “a”, respectively, of the 10-bit encoded data that the transceiver must transmitto the receiving terminal. Figure 2-13 illustrates the TX data map during 8B/10B bypass.During receive when 8B/10B decoding is enabled, the running disparity of the serial transmissioncan be read by the transceiver from the RXRUNDISP port, while the RXCHARISK port indicatespresence of a K-character. When 8B/10B decoding is bypassed, these bits remain as Bits “b” and“a”, respectively, of the 10-bit encoded data that the transceiver passes on to the user logic.Figure 2-14 illustrates the RX data map during 8B/10B bypass.Figure 2-13: 10-Bit TX Data Map with 8B/10B BypassedFigure 2-14: 10-Bit RX Data Map with 8B/10B BypassedUG024_10a_0516027 8 9654320 1First transmitted Last transmittedTXCHARDISPMODE[0]TXCHARDISPVAL[0]TXDATA[7] . . . . . . TXDATA[0]g h jfiedca bUG024_10b_0516027 8 9654320 1First received Last receivedRXCHARISK[0]RXRUNDISP[0]RXDATA[7] . . . . . . RXDATA[0]g h jfiedca b
