Camera Link

Camera Link is a serial communication protocol standard designed for computer vision applications based on the National Semiconductor interface Channel-link. It was designed for the purpose of standardizing scientific and industrial video products including cameras, cables and frame grabbers. The standard is maintained and administered by the Automated Imaging Association or AIA, the global machine vision industry's trade group.

Transmission protocol

Camera Link uses one to three Channel-link transceiver chips with four links at 7 serial bits each. At a minimum, Camera Link uses 28 bits to represent up to 24 bits of pixel data and 3 bits for video sync signals, leaving one spare bit. The video sync bits are Data Valid, Frame Valid, and Line Valid. The data are serialized 7:1, and the four data streams and a dedicated clock are driven over five LVDS pairs. The receiver accepts the four LVDS data streams and LVDS clock, and then drives the 28 bits and a clock to the board. The camera link standard calls for these 28 bits to be transmitted over 4 serialized differential pairs with a serialization factor of 7. The parallel data clock is transmitted with the data. Typically a 7× clock must be generated by a PLL or SERDES block in order to transmit or receive the serialized video. To deserialize the data, a shift register and counter may be employed. The shift register catches each of the serialized bits, one at a time, then registers the data out into the parallel clock domain - once the data counter has reached its terminal value.