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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.