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+                        Programmer's View of Cpia2
+
+Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a
+division of ST Microelectronics).  There are two versions.  The first is the
+STV0672, which is capable of up to 30 frames per second (fps) in frame sizes
+up to CIF, and 15 fps for VGA frames.  The STV0676 is an improved version,
+which can handle up to 30 fps VGA.  Both coprocessors can be attached to two
+CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor.  These will
+be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors.
+
+The two chipsets operate almost identically.  The core is an 8051 processor,
+running two different versions of firmware.  The 672 runs the VP4 video
+processor code, the 676 runs VP5.  There are a few differences in register
+mappings for the two chips.  In these cases, the symbols defined in the
+header files are marked with VP4 or VP5 as part of the symbol name.
+
+The cameras appear externally as three sets of registers. Setting register
+values is the only way to control the camera.  Some settings are
+interdependant, such as the sequence required to power up the camera. I will
+try to make note of all of these cases.
+
+The register sets are called blocks.  Block 0 is the system block.  This
+section is always powered on when the camera is plugged in.  It contains
+registers that control housekeeping functions such as powering up the video
+processor.  The video processor is the VP block.  These registers control
+how the video from the sensor is processed.  Examples are timing registers,
+user mode (vga, qvga), scaling, cropping, framerates, and so on.  The last
+block is the video compressor (VC).  The video stream sent from the camera is
+compressed as Motion JPEG (JPEGA).  The VC controls all of the compression
+parameters.  Looking at the file cpia2_registers.h, you can get a full view
+of these registers and the possible values for most of them.
+
+One or more registers can be set or read by sending a usb control message to
+the camera.  There are three modes for this.  Block mode requests a number
+of contiguous registers.  Random mode reads or writes random registers with
+a tuple structure containing address/value pairs.  The repeat mode is only
+used by VP4 to load a firmware patch.  It contains a starting address and
+a sequence of bytes to be written into a gpio port.
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