Text Mode Display Architecture - Zenith Z-100 Reference Manual

Page ?.10
Video Graphics Programming

Text Mode Display Architecture

A 2-byte character and attribute format is used to define each character display
position as shown in Figure 7.3.
C harac te r
7 6 5 4
Figure 7.3. Character/Attribute Format
These two bytes are mapped into assigned locations in the screen memory buffer,
which is part of the video interface not the system memory. Table 7.2 shows
the codes assigned to the particular character attribute desired for a monochrome
display. The starting address (character byte) must be an even numbered location.
Table 7.2. Monochrome Character/Attribute Selection
FUNCTION
Normal video
Reverse video
Nondisplay (black)
Nondisplay (white)
Underline (normal, if enabled)
If B (bit 7) is logic I, foreground blinks
If I (bit 3) is logic I, foreground is intensified
Note that bits 0 through 2 and bits 4 through 6 are either all logic I (white)
or all logic 0 (black) in the monochrome submode with the exception of the
underline function. All other combinations of these bits are used to obtain the
desired foreground and background colors on an RGB monitor or levels of gray
on a monochrome monitor.
B y t e ( M )
3 2 1 0 7
ATrRIBUTE BYTE (BITS)
7 6 5 4 3 2 I 0
B 0 0
B I
B 0 0
B I I I I I I I
B I 0 0 I
A ttr i b ut e B y t e ( M+t )
6 5 4 3
0 I I I I
I I I 0 0 0
0 I 0 0 0
I I I
2 1 0