Video display processor

Abstract

A video display processor (VDP) is connectable to an input control device such as a light pen and a mouse. The VDP comprises a counter circuit which is composed of an X counter and a Y counter. When a mouse mode is selected, X and Y pulse signals are supplied to the X and Y counters so that the contents of the X and Y counters represent the amount of movement of the mouse. When a central processing unit (CPU) connected to the VDP reads the contents of the X and Y counters in this mouse mode, the X and Y counters are reset. When a light pen mode is selected, the X and Y counters effect a count operation of a clock signal generated in the VDP in synchronism with the display of image on a screen so that the contents of the X and Y counters represents X-Y coordinates of a display element which is currently displayed on the screen. The CPU reads the contents of the X and Y counters in response to a light detection signal outputted from the light pen thereby to input the X-Y coordinates of the display element selected by the light pen. In a collision detection mode, the counter circuit effects the same counting operation as that effected in the light pen mode. The CPU reads the contents of the X and Y counters in response to a collision detection signal, which is generated by an associated circuit when animation patterns of the video image displayed on the screen overlap, thereby to input the X-Y coordinates of the collision position.