Dalsa X64-AN Quad User Manual
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X64-AN Quad User's Manual Theory of Operation 45Serial PortX64-AN Quad hosts 4 serial ports intended for camera control only. Due to data flow multiplexing ofthe 4 serial ports, only one serial port can communicate at one time. Data received from a camera willalways be sent to the last serial port that sent characters. See section “J19: Strobe & Com Ports” onpage 69 for pinout information.The default names for the serial ports are: X64-AN Quad_X_Serial_Y, where X represents the X64-AN Quad board number from 1 to 8, and Y represents the serial port number from 0 to 3.Note: A typical configuration would use 9600 baud8-bitno parity1 stop bit (9600-8-N-1).Ports can be used with their default names (for example: X64-AN Quad_1_Serial_0) by many cameracontrol applications. Additionally, the serial port can be mapped as a standard Windows COMx portfor convenience or compatibility with any communication program (such as HyperTerminal).Acquisition ProcessThe following sections describe the various acquisition stages of the X64-AN Quad. Composite analogvideo input from cameras or any other source can be processed in both the analog domain before theA/D stage and in the digital domain before transfer to host system frame buffers.Anti-aliasing FilterFollowing a differential input buffer stage, the video passes through a low-pass filter, optimized forstandard video frequencies with a filter corner set to 12.87 MHz. When acquiring video from non-standard sources, the low-pass filter can be bypassed with a manually set jumper (see “J8, J9, J10, J11:Input Low Pass Filter Select” on page 65). Each of the four inputs has its own low-pass filter bypassjumper.The low-pass filter strips high frequency signal content from the incoming video signal, to avoidsampling aliasing artifacts. Standard video (RS-170, CCIR) has useful frequency content up toapproximately 6MHz. Frequencies above this can be eliminated using the low-pass filter. Samplingrates for standard video are 10MHz to 14MHz. If frequencies at or above the sampling rate are presentin the input, they represent noise rather than useful video. These frequencies can “alias” into the realvideo signals causing corruption. The low-pass filter eliminates any high frequency signal contentbefore digitization. See “Input Block Diagram (one shown)” on page 5. |
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