RocketIO™ X Transceiver User Guide www.xilinx.com 99UG035 (v1.5) November 22, 2004 1-800-255-7778Output Swing and Emphasis RAC CoupledWhen the transmit output and receive input of two MGTs are AC coupled and/or thereceiver is differentially terminated, the transmitter sees an AC impedance of25Ω (50Ω ||50Ω). However, the DC impedance is now 50Ω, thus changing the commonmode voltage from the DC coupled case. The drive/emphasis settings for supported single-ended output swing (Vos) and pre-emphasis levels (%, dB) when AC coupled are shown inTable 4-4. The unused (grey) combinations are not supported and should not be used.Table 4-4: Output Swing versus Pre-Emphasis (AC Coupled)TXDOWNLEVEL0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15TXEMPHLEVEL0 120mV0%0.0dB180mV0%0.0dB240mV0%0.0dB300mV0%0.0dB360mV0%0.0dB420mV0%0.0dB480mV0%0.0dB1 150mV40%2.9dB210mV29%2.2dB270mV22%1.7dB330mV18%2.9dB390mV15%1.2dB450mV13%1.1dB2 120mV100%6.0dB180mV67%4.4dB240mV50%3.5dB300mV40%2.9dB360mV33%2.5dB3 150mV120%6.8dB210mV86%5.4dB270mV67%4.4dB330mV55%3.8dB4 120mV200%9.5dB180mV133%7.4dB240mV100%6.0dB5 150mV200%9.5dB210mV143%7.7dB6 120mV300%12.0dB789101112131415
