Graphics Storage Map; Medium Resolution Mapping - Zenith Z-100 Reference Manual

Page 7.12
Video Graphics Programming
Medium Resolution (320 x 200) Graphics
Pixel information is stored in video memory in two banks of 8000 bytes each,
as shown in Figure 7.4. Address B8000 contains color selection data for the pixels
in the upper left corner of the display area. Addresses B8000 to B9F3F contain
information for pixels in even numbered rows 0 through 198. Addresses BA000
to BBF3F contain information for odd numbered rows 1 through 199.
Memory Address
6 80 0 0
B9F3F ~
69FFF ~
BBF3F ~
Each video memory byte contains color information for four pixels in 2-bit pairs
as in the format shown in Figure 7.5.
Figure 7.5. Medium Resolution Mapping
Figure 7.4. Graphics Storage Map
7 8 5 4
C1 C O C1 CO C1 CO
e ven sc ans ( 0 , 2 , 4 , . . . 1 9 8 )
( 8000 b y t e s )
( 1 , 3 , 5 , . ..199)
o dd s c a n s
( 8000 b y t e s )
3 2 1 0
C1 CO
0