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18
Theory of Operation
Revision 1.1
Phoenix PC-1280 USB Digital Camera User’s Guide
Fixed Pattern
Compensator
If the Fixed Pattern Compensation is turned ON, the pixel from the
sensor is subtracted by the Fixed Pattern (Black Frame with the
fixed pattern associated with a particular sensor chip). The resultant
image has a reduced fixed pattern noise.
10 Bit LUT
A single bank 10 Bit LUT is provide in the pixel data path to sup-
port simple processing such as gamma correction or negative vid-
eo, etc. This LUT is used as a 10 to 8 mapping, if the 8 bit pixel
mode is selected. The LUT could be by passed if desired.
Color Space
Convertor
In this stage, the monochrome pixel is converted into YUV format,
with the U/V byte filled with 0x80. The YUV format provide con-
venient way to display on a Overlay Surface when DirectDraw is
used.
For the PC-1280/C Camera, the Bayer Patterned color pixels are
converted into RGB format (24 bit/pixel). Or they can be converted
into YUV(16 bit/pixel) format. The conversion is done by hard-
ware to reduce the burden of software conversion. However, this
results in higher data traffic on the USB Bus.
The user can decide on the right pixel format for the application. If
desired, the conversion stage may be bypassed.
SDRAM Buffer
The memory buffer provides multiple functionality. The Fixed Pat-
tern Frame is stored here and is read out to be operated with the in-
coming pixels. The captured frame(s) in all pixel formats are stored
here. When the USB Bus is ready, they are read out from this buffer
and sent to the USB.
Capture Control
The Capture Control Block determines when, how and where to
store the pixel data (after the Color Space Conversion) in the mem-
ory buffer. The user can control full or partial (ROI) frames cap-
tured. The user also specifies how the capture is done; single,
continuous or sequence capture.
Transfer Control
This block controls the data transfer through the USB Bus. It take
the frames stored in the memory buffer and puts them into USB
packets. Then according to the user’s command, the packets are
transferred via the USB protocol. The capture of a frame and the
transfer of it can therefore be separated if desired.
Miscllaneous
Control
This control handles other minor tasks, such as interfacing with the
Trigger and Strobe signals, generating the events to the user pro-
grams and control the sensor chip exposure time (when Global Ex-