| 摘要 |
<p>For each row of characters to be displayed the characters and associated attribute information (underine, flashing, etc.) are transferred to buffers 161-164 on bus 191 from the terminal memory. The characters are then converted by a character generator 253 and shift registers 271 to a VIDEO signal for a monitor 180 during the raster lines pertaining to the row, counted off by a raster counter 254. The characters are stored as strings in the memory in correct character order but arbitrary row order. Associated row designators include the address of the first character to be displayed in the row, a pointer address to the next designator the number of the first raster line of the row to be displayed and the number of lines to be displayed. At the end of the last line of each row the newly pointed to row designator is transferred to registers which address the first character to be transferred to the buffers 161-164. Horizontal scrolling is effected simply by changing the first character addresses in the designators. Smooth vertical scrolling is effected by progressively incrementing first raster line number and decrementing the number of lines to be displayed (or vice versa).</p> |
