| 摘要 |
PURPOSE:To improve the efficiency of a clipping processing by deciding whether or not an address renewed thereafter exists in a memory space during the renewing of an address and releasing quickly the data writing when the address does not exist. CONSTITUTION:A clipping processing circuit 14, when either of horizontal and vertical addresses XA and YA are projected from a memory space M2 a writing pulse WP to a memory 11 is stopped and the data writing is stopped. During the first renewing period of a total horizontal address XA, the horizontal address XA is not present in the memory space M2, and then, at the time of the completion of the renewal, a pulse P7 from an address generating circuit 12 is outputted as a writing releasing signal S6 from an OR circuit 154. Further, when the renewing direction of the vertical address is the upper direction (lower direction), a Y coordinate value corresponding to the vertical address during the renewing presently is positive (negative) and a Y coordinate value is a point outside an image display area, the total input of an AND circuit 159 comes to be H, the output signal S6 of the OR circuit 154 comes to be L and the data writing is released. |
