CRT 8002 & 5037
The 8002 Video (Character) Generator LSI and the 5037
Video/Timer Controller LSI make up the majority of the
video section. The 8002 contains a predetermined character
set, 128 alphanumeric characters and graphic symbols. When
a character is to be output to the CRT, the address of the
character is placed on the address bus of the 8002 by the
microprocessor. When the 8002 is selected, this character
address is input to the 8002. Then, in time with the video
dot clock, the character selected is output in serial fashion
to the CRT.
The only attribute selection used by the Eagle system is
reverse video. When reverse video is selected, the reverse
video line is pulled high and the character data is inverted,
before it is placed in the serial output shift register of
the 8002.
The other part of the video section is the 5037. This LSI
is not pre-programmed. It is programmed with seven 8-bit
words that define for the 5037 the horizontal and vertical
format of the CRT display. This information is stored in
the 2732A Boot EPROM, and loaded as part of the initial
loading sequence. The information includes the size of the
display, the size and spacing of the character blocks, and
the vertical and horizontal scan rate. The 5037 also provides
the cursor mode information to the 8002.