Patent ID: 7397456

Claim:
A control signal inspecting device for a display device for displaying an indication of the existence of an abnormality of plural control signals inputted from an external signal source on the screen of the display device, comprising: a display device for inspection at a resolution equal to or higher than that of said display device; and a display controller having a timing controller having a control signal inspecting circuit for generating control signals including a horizontal synchronizing signal, a vertical synchronizing signal and a display timing signal on the basis of various kinds of synchronizing signals inputted from said external signal source, wherein said control signal inspecting circuit has: a plural-pixel counter for setting a clock corresponding to plural pixels determined in advance to a parameter clock, and counting the pixels corresponding to the number of parameter clocks; a decoder for converting each of the horizontal synchronizing signal, the vertical synchronizing signal and the display timing signal as said control signals into red (R) data, green (G) data and blue (B) data; a delay circuit for delaying each of said control signals by a constant time; a shift register having the capacity of said parameter clocks for storing each of said control signals delayed by said delay circuit; a line memory having the capacity of about the resolution of said display device for inspection in the horizontal direction, and respectively converting output data of said shift register into red (R) data, green (G) data and blue (B) data by said decoder and storing the converted data; an address counter for designating the address of an input port when each output data of said decoder are stored to said line memory; an end register for storing a final address of said address counter; a start counter for designating an output address of said line memory in accordance with the stored data of said end register; and a data control circuit arranged on the output side of said line memory and comparing the stored data of said address counter and said end register, and selecting the red (R) data, the green (G) data and the blue (B) data outputted to said display device and its brightness by the comparison result.