Resolution, Scatter/Gather, Symptom

A modern digital frame grabber should be able to convert data from cameras with each of these formats into scan line ordered images in system memory.

Resolution

The ability of a camera to resolve details in a scene is dependent on the type of lens employed and the relation of the camera to the scene. Therefore manufacturers often describe the resolution of a camera by the stating number of horizontal and vertical picture elements contained in the image sensor. For example, the Pulnix TM1300 area-scan digital camera has 1300 picture elements in each row by 1030 rows.

Scatter/Gather

Traditionally to get a contiguous block of memory in Windows 95 you had to use a kernel level driver to capture the memory at power-on boot time. When your application was done the memory couldn't be used by other applications until the computer was rebooted without the contiguous block memory request.

On the other hand, requesting contiguous memory in an application at run-time allows the memory to be freed up to other applications when the requestor is finished. But large contiguous blocks of memory might not be available at run- time because as a computer opens and closes applications the memory gets fragmented into smaller blocks.

A frame grabber that supports scatter/ gather uses small blocks of memory as if it has a large contiguous block. It does this by building a table of addresses of the small blocks and stepping through the table to fill them with the completed image, so that it appears to the application as one large block.

Troubleshooting

Symptom:

Black Screen Where Image Should Be

Possible Cause/Solution:

•Verify that the data lines and at a minimum the HDV, LDV, and CAMCLK (Pixel Clock) are connected correctly on the cable. If the Camera is providing the Pixel Clock (most common) then the CAMCLK (pins 65 & 15) will be used. If the Frame grabber is providing the Pixel Clock, then the Synthclk (pins 57 & 7) will be used.

•Verify that the power is properly connected to the camera. If the camera is being powered off the board, then make sure the power pins are connected in the cable and that the 12 volt floppy power connector is connected to the J1 connector on the PCD1000.