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(11) | EP 0 069 518 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Raster scan video display terminal and method of operation |
| (57) For each row of characters to be displayed the characters and associated attribute
information (underline, 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). |