CRT Display device

DETAILED DESCRIPTION The disadvantages of the prior art are overcome with the present invention and an improved display control system for use in a CRT display device is provided.
In accordance with one aspect of the present invention, a raster scanning type CRT display device comprises a character pattern generator for generating a dot pattern signal; a shift register for converting said dot pattern signal into a video signal which is to be applied to a CRT; a clock generator for supplying a clock pulse signal to said shift register; and frequency adjusting means connected to said clock generator for changing the clock pulse frequency of said clock generator, thereby characters are displayed in desired width size and pitch depending on the location of the display area of CRT.
Preferably, the clock generator includes a plurality of different frequency components and one of the components is selected by said frequency adjusting means depending on the location of the display area.
A mode selection signal is supplied to the frequency adjusting means thereby timing of changing the clock pulse frequency of the clock generator is determined in response to a particular mode selected.
The frequency adjusting means preferably comprises a character counter and a counter selector, and the mode selection signal is supplied to the counter selector.
The clock generator preferably comprises a fundamental oscillator, a clock counter and a clock selector.
Alternatively, the clock generator may be comprised of a fundamental oscillator and a programmable clock counter.
The frequency adjusting means may be comprised of a column counter and a counter controller wherein a particular region of the display area of CRT, which is defined by the character columns previously set in the column counter, is scanned with a frequency different from that of the other display region.
It is further preferable to supply a cursor address signal to the present display control system so that characters in the region of interest in the display area of CRT may be displayed in the standard format at all times