Channel Link

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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.

Channel-Link Chipset Block Diagram

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.

System applications[edit]

Camera Link is the biggest application for Channel-Link in 2009. It uses the 28-bit Channel-Link version and specifies for a clock rate up to 85 MHz for a total throughput of 2.38 Gbit/s. It also has a provision for placing 3 chipsets in parallel for a total throughput over 7 Gbit/s.

Telecommunication access-aggregator equipment is another popular Channel-Link application. For example, second generation (2G) and 2.5G mobile phone base stations use Channel-Link to transfer data between radio cards and baseband processing cards. It also provides for the equivalent data transfers in DSL and multiservice access multiplexors.

Multi-function printers are another major application for Channel-Link. It transfers the data over cables between the modules inside the printers. For example, the scanner module sends image data streams to the processing engine module.

Because Channel-Link is a general-purpose data pipe with no overhead for protocol or encoding, there are many more system applications for this efficient data transfer technology.

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