Writing Data To The Z-329 Card - Zenith Data Systems Z-100 Series Installation Manual

Page
4.2
Software Considerations
Table 4.1 (continued). Video Control Register Functions
BIT
NUMBER
DB4
DB5
DB6/DB7
SIGNAL
NAME
PAGE
BLKEN
FONT 0/
FONT 1
BIT
VALUE
o
o
x
FUNCTION
This allows the first page of memory to be
displayed.
Pages the display to the second page of the
display. This feature can be used only if the
optional 8K x 8 RAMs are installed.
This allows the blink attribute bit in the attri-
bute RAM to control the background intensity
of the display.
This allows the blink attribute bit to control
the blinking of the character.
These bits control the font in use FONT 1
by the display. The font selection follows a
standard binary count (00
=
font 0, 01
=
font 1, 10
=
font 2, 11
=
font 3). Fonts 2
and 3 can be used only if the optional 128K
ROM is installed.
To initialize the card, write the bits 0001 XX1 into I/O port 3B8.
Writing Data to the Z-329 Card
NOTE: Bit 0 in the control register must be 1 to enable the write function.
Before attempting to write to the memory, be sure this bit is properly set.
The display is treated by the CPU as RAM. The text and control data
is written into the RAM on the 2-329 Card. The CRTC and hardware
on the card manage the display. The programmer has a number of options
in the way that data can be handled.