ADVANCE INFORMATION
VCT 38xxA
3.11.OSD Layer
Apart from the WST layer, there is an additional OSD
layer on chip. The OSD layer accesses the CPU mem-
ory via DMA to read text, display attributes, and char-
acter font information. The color outputs of the OSD
layer can have higher priority than the WST layer out-
puts. Thus, it is possible to overlay the teletext display
with an additional layer for user guidance (see Fig. 3–
19).
Code
01
Function
Underline On
Underline Off
Flash On
Notes
only for 13 scanlines/character
02
03
04
Flash Off
05
Italics On
06
Italics Off
Transparent
Shadow
07
layer becomes transparent
08
layer becomes transparent and
contrast is reduced to 66%
Full Screen Layer
0C
0D
END
CR
end of layer
end of text line
0E − 7F ASCII Character using font 1 or font 2
80 − FF Control Code
Only one control code per character
WST Layer
is allowed. Depending on OSD
Mode, the control code defines
either color or character set.
Color
bit 0 = foreground color blue
bit 1 = foreground color green
bit 2 = foreground color red
bit 3 = background color blue
bit 4 = background color green
bit 5 = background color red
bit 6 = replace white by transparent
bit 7 = 1
OSD Layer
Character Set
bit 0 = bit 7 of character code
bit 1 = bit 8 of character code
Fig. 3–19: Display layer
bit 2 = bit 9 of character code
bit 3 =
bit 4 =
bit 5 =
The OSD layer reads text strings addressed by a pro-
grammable text pointer. Codes smaller than 80h will
address the character font, codes greater or equal 80h
are interpreted as control codes to change color or
character set (see Table 3–14). After reading a control
code the OSD layer will do an additional read to get the
next character code.
bit 6 = latching shift to character set
bit 7 = 1
Shaded attributes are default at start of each text line.
Micronas
67
MICRONAS [ MICRONAS ]
