| 摘要 |
PURPOSE:To execute the initialization of a hidden-surface erasing circuit for only a small optional area not for the whole of a display area by generating the X address and the Y address of the small optional area. CONSTITUTION:When only a rectangular area at a part on a picture plane is initialized, an X1 is loaded on a register A81 and an X counter 82, and an X2 on a register B83, and a Y1 on a Y counter 85, and a Y2+1 on a register C86 respectively for a coordinate (X1, Y1) at a left upper corner and a coordinate (X2, Y2) at a right lower corner in the rectangular area. And the X counter 82 is counted up until it coincides with the value (X2) of the register 83, and a count is terminated when they are coincided, and 1 is added on the value of the Y counter 85. Simultaneously, the value (X1) of the register 81 is loaded on the X counter 82, and the same operation is repeated hereafter. And by continuing the operation until the value of the Y counter 85 is coincided with the value of the register C86, the X address and the Y address of the area to be initialized are generated. |
