Camera Link is a camera interfacing specification developed by the camera and frame grabber community to simplify camera/frame grabber interfacing and qualification. The Camera Link specification defines:

  • A standard connector that will be used on both the camera and the frame grabber.
  • A standard cable to connect the camera and the frame grabber.
  • Image formats for transmitting data from the camera to the frame grabber.
  • Standard camera control inputs.
  • A standard method for transmitting serial communication data between the camera and the frame grabber.
  • A standard chip set (Channel Link by National Semiconductor) that will be used in the camera and frame grabber for data transfer.

Camera Link is based the Channel Link LVDS chip set manufactured by National Semiconductor. A Channel Link chipset consists of a transmitter, DS90CR287, and a receiver, DS90CR288A, and is used to transfer digital data. The chipsets have a 3.3V supply and operates with a clock speed of 85 MHz. The transmitter converts 28 bits of CMOS/TTL data into four LVDS data streams. The data is sampled and transmitted with every cycle of the transmit clock. The receiver converts the LVDS data streams back into 28 bits of CMOS/TTL data. Using a transmit clock with a frequency of 85 MHz, 28 bits of TTL data is transmitted at 595 Mbps per LVDS channel. With four data channels the total data throughput is 2.38 Gbit/s. In the Channel Link protocol 28 bits of data are transferred over just 4 pairs of wires and a fifth pair is used to transfer a required clock signal. The basic outline of the chip functionality is diagrammed below

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CAMERA LINK

Camera link uses the National Semiconductor's Channel Link chips as shown above to define the interface. Using one or two transmitter or receiver Channel Link chips, the standard defines a Basic, Medium, and Full Camera Link specification. Thus allowing up to approximately 800-900 MB/sec transfers at 85 MHz. This interface hierarchy is diagrammed below.

click to enlarge


DS90CR287 OVERVIEW

The DS90CR287 transmitter converts 28 bits of LVCMOS/LVTTL data into four LVDS (Low Voltage Differential Signaling) data streams. A phase-locked transmit clock is transmitted in parallel with the data streams over a fifth LVDS link. Every cycle of the transmit clock 28 bits of input data are sampled and transmitted. At a transmit clock frequency of 85 MHz, 28 bits of TTL data are transmitted at a rate of 595 Mbps per LVDS data channel. Using a 85 MHz clock, the data throughput is 2.38 Gbit/s (297.5 Mbytes/sec). Both devices are also offered in 64 ball, 0.8mm fine pitch ball grid array (FBGA) package which provides a 44% reduction in PCB footprint over the 56L TSSOP package.

This chipset is an ideal means to solve EMI and cable size problems associated with wide, high-speed TTL interfaces.

FEATURES

  • 20 to 85 MHz shift clock support
  • 50% duty cycle on receiver output clock
  • 2.5 / 0 ns Set & Hold Times on TxINPUTs
  • Low power consumption
  • ±1V common-mode range (around +1.2V)
  • Narrow bus reduces cable size and cost
  • Up to 2.38 Gbps throughput
  • Up to 297.5 Mbytes/sec bandwidth
  • 345 mV (typ) swing LVDS devices for low EMI
  • PLL requires no external components
  • Rising edge data strobe
  • Compatible with TIA/EIA-644 LVDS standard
  • Low profile 56-lead TSSOP package
  • Both devices are also available in 64 ball, 0.8mm fine pitch ball grid array (FBGA) package

DS90CR287 OVERVIEW

The DS90CR287 transmitter converts four LVDS (Low Voltage Differential Signaling) data streams into 28 bits of LVCMOS/LVTTL data. A phase-locked transmit clock is transmitted in parallel with the data streams over a fifth LVDS link. Every cycle of the transmit clock 28 bits of input data are sampled and transmitted. At a transmit clock frequency of 85 MHz, 28 bits of TTL data are transmitted at a rate of 595 Mbps per LVDS data channel. Using a 85 MHz clock, the data throughput is 2.38 Gbit/s (297.5 Mbytes/sec). Both devices are also offered in 64 ball, 0.8mm fine pitch ball grid array (FBGA) package which provides a 44% reduction in PCB footprint over the 56L TSSOP package.

This chipset is an ideal means to solve EMI and cable size problems associated with wide, high-speed TTL interfaces.

FEATURES

  • 20 to 85 MHz shift clock support
  • 50% duty cycle on receiver output clock
  • 2.5 / 0 ns Set & Hold Times on TxINPUTs
  • Low power consumption
  • ±1V common-mode range (around +1.2V)
  • Narrow bus reduces cable size and cost
  • Up to 2.38 Gbps throughput
  • Up to 297.5 Mbytes/sec bandwidth
  • 345 mV (typ) swing LVDS devices for low EMI
  • PLL requires no external components
  • Rising edge data strobe
  • Compatible with TIA/EIA-644 LVDS standard array (FBGA) package

    • SOFTWARE INTERFACE

    The Camera Link specification defines a DLL as outlined in the Camera Link API. All Camera Link compliant frame grabbers provide a dll file named clser***.dll, where *** is specific to the frame grabber vendor. There are four functions within that .dll:

    • clSerialInit—Initialize the serial communication for a specific board.
    • clSerialRead—Read bytes from the camera.
    • clSerialWrite—Write bytes to the camera.
    • clSerialClose—Close the serial communication.

    Thus the FastCamera13 and FastCamera40 which have Camera Link compliant output modes can be interfaced with any Camera Link compliant frame grabber.

    Click Here to download datasheet or Here to register to download manuals.

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