| 摘要 |
PURPOSE:To write subordinate image data while main image data of a memory plane are saved by inhibiting the subordinate image data from being written in addresses wherein effective data are already written. CONSTITUTION:Read data read out of the memory plane 20 are temporarily stored in the register 21-1 of a data presence/absence detection part 21. A write enable signal 24 is inputted to the AND gate 22-1 of a subordinate write control part 22 and outputted to the memory plane 20 only when a signal inputted from the register 21-1 is at a low level. When the main image data stored in the register 21-1 are effective data (high-level data), the write enable signal 24 is not inputted to the memory plane 20 even if the subordinate image data 12 are inputted to the memory plane 20. Therefore, the subordinate image data are not written in the memory plane 20 and the main image data which are already written are saved. |
