Vector 4 - Page 77

EXHIBIT II-11 SCAN LINE GENERATION
TERMINOLOGY
1l_Screen
Character Columns
Character
B
1
2eeceececsncsccasnconcscones
79
Rows
.
¢
l
3
1
2
D
¢12..,.‘.’ ..................... 79
8 ]
1
2
3
1 Scan Line
L Character @1 2V .................... 79
Lell
gL ]
¢g ...... 15
3
1 Scan line of
1 Character Cell
Y ~
LTI iiil] 16 1/2 Dots
Character Character
Rows Columns
24 80
Character Scan
Cells Lines
Per Screen| Per C. Row Per C. Row | Per C. Cell
1920 80 13 13
* 60 Hz Systems
EXAMPLE: Scanning of CRT starting
immediately after vertical retrace
period.
1.
CRT transmits "0" Scan Line of
first Character Cell of
Character Row "Q",
CRT transmits "0" Scan Line of
second Character Cell of
Character Row "(Q",
This cycle continues for entire
"0" Scan Line.
L0-L3 lines (from Video
Controller) is incremented.
CRT transmits "1" Scan Line of
first Character Cell of
Character Row "Q",
CRT transmits "1" Scan Line of
second Character Cell of
Character Row "0",
This cycle continues for entire
"i" Scan Line.
CRT continues transmitting scan
lines in this fashion until L3-L0
has counted to 13;9. When this
occurs the Video Controllers RA
Register is zeroed and a new
Character Row (Row "1") is
indexed in RAM.
I 3-14