| 摘要 |
PURPOSE:To exactly plot an overlapped image by performing OR write by read modify write in addition to overwrite when performing the write of a color binary image into the address of a memory. CONSTITUTION:A one preceding address (a) is compared with a present address (b) by an address comparator 11 and when the present address is smaller than the one preceding address, a discrimination signal RMW to decide whether the read modify write is performed or not is outputted. At the same time, an OR processor 12 ORs preceding data (d) and present data (c). As data to be written in a memory 10, data passing the device 12 or through data are selected by a selector 13 corresponding to the RMW signal. When the RMW signal shows the 'execution of read modify write', data obtd. by ORing the preceding data and the present data are written in the memory 10. Thus, when it is desired to plot the binary color image while overlapping it onto the address, the color of a preceding image and a color plotted later can be plotted while being overlapped. |
