IBM RT Series Hardware Reference Manual page 349

TNL SN20-9844 (March 1987) to 75X0235
The X, Y, DX and DY parameters are specified in the queue load. Not all parameters need be
specified for each graphic operation. Only the parameters that change from graphic operation to
the next need be specified. See register contents at completion of graphic operation. An example
of a queue load that clears a 1024 x 768 pel screen is shown below. Note that a hex value of
'000' represents a value of 1024 pels both for X and DX. The same is true for Y and DY.
Queue Queue
Action By
Register Register
Reg
Address Data Queue Processing Start Min Max End
Que Ptr X'7000' Load X into R 7 X= 1024 1 1024 X
Que Ptr-l X'6300' Load Y into R6
Y=768
1 1024 Y
Que Ptr-2 X'9000' Load DX into DX= 1024 1 DX= DX
R9 X
Que Ptr-3 X'8300'
Load DY into DY=768 1 DY=
DY
R8 Y
Que Ptr-4 X'D2FO' Execute Graphic
Operation
Note: Unpredictable results might occur if DX
>
X or DY
>
Y.
Extended Monochrome Graphics Adapter 37