The DS42BR400 is a quad 250 Mbps 4.25 Gbps CML transceiver, or 8-channel buffer, for use in XAUI Fibre Channel backplane and cable applications. With operation down to 250 Mbps, the DS42BR400 can be used in applications requiring both low and high frequency data rates. Each input stage has a fixed equalizer to reduce ISI distortion from board traces. The equalizers are grouped in fours and are enabled through two control pins. These control pins provide customers flexibility in XAUI applications where ISI distortion may vary from one direction to another. All output drivers have four selectable steps of de-emphasis to compensate against transmission loss across long FR4 backplanes. The de-emphasis blocks are also grouped in fours. In addition, the DS42BR400 also has loopback control capability on four channels. All CML drivers and receivers are internally terminated with 50 pull-up resistors.