General Theory Of Operation; Memory Organization; Ram - Zenith Data Systems Z-100 Series Installation Manual

Chapter 3
General Theory of Operation
The Z-329 Monochrome Video Card produces 25 rows of 80 characters.
The computer system transfers alphanumeric characters to the Z-329 Card
in ASCII code. The character and an attribute byte are stored in the RAM
on the Z-329 Card. When the character is to be displayed, the CRTC
addresses the memory and a character ROM decodes the ASCII data
into pixel lighting instructions.
Memory Organization
RAM
The memory supplied on the Z-329 consists of two 2K x 8 static RAMs.
One RAM IC is used to store the character in ASCII code and the other
stores the attribute associated with this character. The standard memory
allows one page of text to be stored. The memory is arranged linearly
(characters are stored sequentially in order of use) with no unused mem-
ory.
Optional 8K x 8 static RAMs may be installed, giving the Z-329 Card
the capability of addressing up to two pages of text with an interlaced
display.