IBM RT Series Hardware Reference Manual page 353

TNL SN20-9844 (March 1987) to 75X0235
Rectangular Copy/Merge (X'30')
The rectangular copy/merge graphic operation reads a source rectangle defined by XS, YS, DX
and DY writes a destination rectangle defined by XD, YD, DX and DY as shown below. Any
type of overlapping source and destination combinations are allowed. The YD register is
preserved during graphic operation type X'30'.
DESTINATION RECTANGLE
exclusive (XD, YD)
SOURCE RECTANGLE
~----------------------------~
] - DELTAY
+
1
~
IDYl
(XS, YS) LOWER RIGHT CORNER
I
exclusive
~--------------T-------------~
DELTA X
+
1
=
(OX)
Figure 27. Copy Overlapped Character Line
To achieve a rectangular copy, the logical function (subtype) must be set to X'9'.
In consecutive repeated copy operations (graphic operations type 30) to locations with a
constant destination Y coordinate, the destination Y coordinate need only be specified in the
first queue load since its entry value is preserved. This speeds up the copy execution since only
6 parameters instead of the usual 7 need to be processed. An example of a general use for this
preservation of the destination Y value is in the copying of character images from the display
hidden area to a single horizontal character line in the active display area.
Extended Monochrome Graphics Adapter 41