Function Code 3 — Read Cursor Position - Zenith Z-100 Reference Manual

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Video Graphics Programming
Function Code 3 — Read Cursor Position
Upon return from this call, DH will contain the cursor row, and DL the cursor
column position.
Function Code 4 — Read Light Pen Position
Upon return, AH will contain the light pen trigger/switch status, 0 or 1. If AH
is 0, the light pen has either not been triggered, or not been switched active.
If AH is I, then DH will contain the row, and DL the column where the light
pen was detected. The scan line number (0 to 199) will be in CH, and BX will
hold the pixel column (0 to 319 or 0 to 639, depending on graphics mode).
Function Code 5 — Select Active Display Page
In any text mode, the unused portion of video memory, if any, may be used
for storage of video pages in excess of the current page. In video modes 0 and
I, the valid page numbers are 0 to 7; in modes 2 and 3, allowable values are
0 to 3. In the graphics modes, only page 0 is allowed. Load the page number
into AL
Function Code 6 — Scroll an Area of the
Screen Up
This code allows you to define an area of the screen to be scrolled upward a
desired number of lines. CX is loaded with the upper left-hand coordinates (row
in CH, column in CL), and DX with the lower right-hand coordinates. Load the
attribute byte for blank lines in BH. Load AL with the number of lines to scrolL
If AL is 0, the entire designated window will be deared.
NOTE: If hardware or smooth scrolling are enabled when this function is im-
plemented, they will be activated by this call if the entire screen is scrolled. It
is not possible to use hardware or software scrolling on a portion of the screen.