Display control 4.1.6. Scroll area (possible only with KDT 635) After switching on, the write area of the screen is the so-called scroll area. If this is left by means of cursor control commands (line feed in the last screen line etc.) the contents of the screen moves one line up or down. This is called "scrolling" the screen. The line range of the scroll area can be altered by special com- mands, however. During normal operation, the scroll area can only be left with absolute, but never with relative, cursor pos- ition. In one special case, i.e. the origin mode, the scroll area cannot be left by any positioning command.
In this case, the "upper left screen corner" (cursor position 0,0) is in the upper left cor- ner of the scroll area. If, in the origin mode, the scroll area is re-defined, a home jump of the cursor may be effected so that the cursor stays in the scroll area. Scroll area programming Hex 1Bh 5Bh Z1 NP 3Bh Z2 NP 72h Decimal 27 91 Z1 NP 59 Z2 NP 114 ASCII ESC ( Z1 NP ; Z2 NP r This command can be used to re-define the scroll area. It then goes from line Z1 to line Z2. The first line of the writing area is line 0. 4 - 15