Page:Gametronics Proceedings.djvu/37

 THE OBJECT-ORIENTED APPROACH

The object-oriented approach offers the following advantages:
 * 1) More objects may be used and the motion of these objects is easier to control.
 * 2) RAM requirements are minimal, thus reducing system cost.

Figure 3 is a block diagram of an object-oriented, microprocessor-controlled game system. The microprocessor reads the game stored in ROM and controls the video presented to the TV. The Object Blocks (OB) serve as a programmable video generator, interpreting microprocessor commands and presenting video to the Video Summer Block (VSB). The VSB accepts digital video signals from the object block and generates either RF for a standard TV Receiver or composite video for a TV monitor.

The microprocessor communicates with, the OB over the address bus and data bus. Basically, the OB looks like part of the memory field to the microprocessor. The microprocessor writes data into the OB's RAM field. The OB, in turn, generates video that reflects the information stored in its control field. The OB also presents the 2650 microprocessor with I/O and status information (e. g., object collisions, etc.) by writing this data into its registers. The microprocessor can then read the I/O and status information data and make decisions accordingly.

To understand how the system operates, we will examine the functions of each individual block.

All timing circuits are generated from a 3.58 MHz clock. The functions of these circuits are twofold:

1)To provide the various sync timings for the vertical and horizontal oscillations of the TV monitor.

2)To provide submultiples of the clock used in more complex signals bearing a synchronous relationship to the movements of the electron beam.