JPS56131283A - Generating circuit of digital color signal - Google Patents

Abstract

PURPOSE:To generate a digital chroma signal with a simple logic circuit by storing the half-period of a carrier chromaticity signal to ROM, and by adding the polarity code according to a sampling signal to the ROM output signal. CONSTITUTION:A chroma signal controlling a hue and chroma saturation from chroma control variable resistor VR1 is converted by A/D converter (a) into a signal which can select the chroma signal, and this signal is used as an address to store ROMd with a chroma level. Further, a sampling clock four times as large as a chrominance subcarrier wave from clock input terminal (b) is counted by counter (c) to output a polarity code signal for every one clock or every two clocks. Then, the chroma level stored in ROMd is applied to adding-subtracting circuit (f) together with the added polarity code signal and at the same time, a luminance signal digitized by A/D converter (e) is applied to circuit (f), which finds the sum or subtraction of both the luminance signal and the chroma level of the digital chroma signal. Then, they are processed by blanking gate circuit (g) to output a digital color signal.