IBM RT Series Hardware Reference Manual page 370

TNL SN20-9844 (March 1987) to 75X0235
Scan Line Sync (X'3D')
The scan line sync graphic operation provides a means of stopping queue processing until a
specified scan line number (SLN) appears in the scan line counter register. The scan line
complement (SLC) is the input data to the scan line sync graphic operation and is the 10 bit 2's
complement of the scan line number.
Note: Valid SLN values are X'OOO' and X'OOI' to X'317. The valid SLC values are X'OOO' and
X'3FF' to X'OE9'. Out of range values cause the adapter queue processing to hang in such a
manner that the adapter must be reset to restore queue processing operation.
Example: Scan Line Sync, stop queue processing until the scan line counter reaches a value of
X'IF5'.
Queue Queue Action
By
Address Data Queue Processing
Calculate SLC
=
10 bit 2's complement of X'IF5'
=
X'20B'
Que Ptr X'A20B'
Load RA with 10 bit scan line complement
Que Ptr-l
X'D3DO'
Execute the scan line sync graphic operation
Graphic Operation Type X'3E' Set Video On
The set video on graphic operation enables the video data line to the display monitor. When the
video data line is enabled, the information contained in the displayable bit map area is displayed
on the monitor.
Example: Set Video On
Queue Queue Action
By
Address Data
Queue Processing
Que Ptr X'D3EO' Execute set video on - Enable the video data line.
58 Extended Monochrome Graphics Adapter