| 摘要 |
<p>Characters stored in a memory 44 are displayed in rows and columns on a display means 11, the rows and columns being counted by a video row counter 49 and a video column counter 45. The address generator 53 for memory 44 includes a roll register 90, the count of which is added (mod the number of rows) to the video row count by a PROM 91, thereby scrolling the display; the PROM 91 is divided into blocks by the video row count, the blocks containing modular addition tables. However, certain blocks are instead filled with just the video row count. This results in the corresponding rows in memory 44 (used for system control information), stored in fixed locations in memory 44, appearing in fixed rows on the display, unaffected by scrolling of the variable data in most of the memory and display. A second PROM 92 combines the adjusted row count with the column count. </p> |
