Graphics Mode; Data Format For Graphic Mode - HP Vectra Reference Manual

Graphics Mode
In the 200 line graphic modes the memory is mapped with even
and odd lines of data in separate banks. Even lines start at offset
OOOOH and odd lines at offset 2000H. Sufficient memory exists for
two pages of graphics to be stored. The second page stores the
even lines at offset 4000H and the odd lines at offset 6000H. In
this mode 25kHz monitors are supported by displaying each of
the 200 lines twice.
In the 400 line graphics mode the memory is mapped into four
banks. Lines 0,4,8, . . . are in the first bank at offset OOOOH.
Lines 1,5.9, . . . are in the second bank at offset 2000H. The
third bank at offset 4000H contains lines 2,6,10,. . . while the
fourth bank at offset 6000H contain lines 3,7,11,etc..
Data Format for Graphic Mode
In the data format mode the 320 x 2 mode maps two bits to each
pixel. Each byte is displayed with the most significant bits to the
left. As shown in the following chart:
D7 D6 D5 D4 D3 D2 D1 DO
u
u uu
C1 CO C1 CO C1 CO C1 CO
C1 and CO select the color as defined by the color register.
640
X
1
The data for the 640 x 1 mode is mapped one bit per pixel with
the most significant bit displayed to the left.
Multi-Mode Video Adapter Card 89