
ON-SCREEN DISPLAY
S3C880A/F880A
13-8
CHARACTER SIZE CONTROL REGISTER (CHACON)
Using the character size control register, CHACON, you can specify four different standard character sizes in
both vertical and horizontal directions. You also use the CHACON register to select rows (0–11) for the character
fade function (see Figure 13-5).
Vertical character size is defined by bits 6 and 7 of the CHACON register; horizontal direction is defined by bits 4
and 5. There are four basic character size settings:
×1, ×2, ×3, and ×4. Size '×1' is the smallest and '×4' is the
largest. For example, to display a '
×1' (horizontal) by '×1' (vertical) size character, you should clear CHACON.4–
CHACON.7 to "0". To display a '
×4' by '×4' size character, you should set bits 4–7 to '1111B'.
You can also combine different vertical and horizontal size selections to produce flattened or elongated
characters (see Figure 13-5).
"1 dot" is a minimum unit of character size. 1 character is composed of 16 dots in width and 18 dots in length. 1
dot in width is 1 fosd clock and 1 dot in length is 1 H-sync line. 1 dot of 1x1 character size (minimum unit) is
composed of 1 fosd clock and 2 H-sync line (even + odd field).
Character size in width is increased by 1 clock. So x1, x2, x3, and x4 in width are the same as 1, 2, 3 and 4
clock, respectively. Character size in length is increased by 2 H-sync line (even field + odd field), so x1 and x2 in
length are the same as 2 H-sync line (even field + odd field) and 4 H- sync line (even field + odd field + even
field + odd field), respectively. Half dot in width is 1/2 fosd clock, and 1/2 dot in length is 1 H-sync line (even or
odd field).
In the fringe and boarder function, 1/2 dot setting can be used. So, please be more careful in using the 1/2 dot to
prevent the blink. (Because the character size is changed in 1 dot unit or set to 1/2 dot in fringing or boarder
function, blinking can occur in interlace scan, so care must be taken when 1/2 dot is used for width.)
OSD Character Size Control Register (CHACON)
F0H, Set 1, Bank 1, R/W
LSB
MSB
.7
.6
.5
.4
.3
.2
.1
.0
Vertical character
size selection bits:
00 = 'x1' size
01 = 'x2' size
10 = 'x3' size
11 = 'x4' size
Fade row address selection bits:
0000 = Row 0
0110 = Row 6
0001 = Row 1
0111 = Row 7
0010 = Row 2
1000 = Row 8
0011 = Row 3
1001 = Row 9
0100 = Row 4
1010 = Row 10
0101 = Row 5
1011 = Row 11
Horizontal character
size selection bits:
00 = 'x1' size
01 = 'x2' size
10 = 'x3' size
11 = 'x4' size
Figure 13-4. OSD Character Size Control Register (CHACON)