Channel-Link (C-Link) by National Semiconductor is a high-speed interface for cost-effectively transferring data at rates from 250 megabits/second to 6.4 gigabits/second over backplanes or cables. National Semiconductor introduced the first Channel-Link chipsets in the late 1990s to provide an alternative to continually widening data buses to get higher throughput.
Channel-Link uses LVDS, and comes in configurations with three, four, or eight parallel data transfer lanes plus the source-synchronized clock for each configuration. In cable applications, it uses one twisted pair in order to transmit a clock signal, and on the remaining differential pairs it transmits digital data at a bit rate that is seven times the frequency of the clock signal. The backplane applications work the same way except for using differential traces instead of twisted pairs.
The three Channel-Link chipset configurations provide varying user interfaces. For example, the three-lane chipset has 21 single-ended inputs and outputs for the user interface, and the four-lane chipset has 28 single-ended inputs and outputs. The eight-lane chipset has 48 single ended inputs and outputs because it uses one of the 7 serialized bits/lane to DC-balance the other six bits.