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As many as 8 analog inputs can be connected of which 4 inputs are used for the input of composite
video or S-VHS brightness signal, 2 color inputs can be used to connect the signal of S-VHS carrier
frequency (chroma). For analog YcbCr signal, the input of the brightness that is selected is used
together with the input of CBIN and CRIN. Automatic gain control works in digital manner. In the
mode of YCbCr ,the gain of chroma channel is fixed and is applicable for 0.7Vp-p nominal amplitude.
However, should there appear ADC overflow, an excessive signal scope 1Vp-p can be selected.
Two ADC (analog-digital conversion) are used to digitalized the input signal. The converter has an
analytic degree of 8 digits. Reference voltage required by the converter is produced by an integrated
band-gap circuit. An adaptive comb filter is used to carry out high quality Y/C separation for
PAL/NTSC signal and to improve the resolution of brightness (band width) and reduce the
interference of color contamination and brightness contamination. Proper programmable limit to the
quantity of characteristic Luma Comb improves the uniformity of 2D resolution. This limitation is set
up by the data of CLIM (turning point).
Color decoder
Processing of both brightness and color is shown here. The color decoder also provides the format
of broad band chroma etc. for the use of S-VHS broad band broad chroma. If self-adaptive comb filter
is used to carry out high quality Y/C separation, then the color decoder conducts the processing in S-
VHS manner. The format of color decoder input is YCrCb 4:2:2. Rear terminal of video frequency
Digital RG B signal can all be converted into analog RGB. It is provided by 3 DAC (digital-analog
conversion), an analog brightness value and another 3 DACs. Its regulation scope is 40% of the
whole RG B.
TV controller
TV controller is composed of CPU,RAM,ROM and some peripheral modules. It includes a memory
module that can access over 64 KB, a pilot installation software allowing for downloading the external
codes into Flash memory. The controller runs a complete set of software required to control TV. The
software includes such control functions as video, OSD and text processing. It also includes the
control for external parts and components such as tuner and stereo decoder. The communication
between the controller and external parts is interfaced by means of I2C bus line(highway) and can
also be connected by the pin at programmable port.
VCT38XXA/B is a single chip TV processing IC for high picture quality. Modular design and
workmanship of sub-micro level enables it to use in all TV equipment. It includes complete display of
video format processing. The video front terminal unit provides an analog interface for all video inputs
and performs analog-digital conversion for the downstream digital video processing.