SAA5281 Datasheet, PDF (27/48 Pages) NXP Semiconductors – Integrated Video input processor and Teletext decoder IVT1.8

Philips Semiconductors
Integrated Video input processor and
Teletext decoder (IVT1.8*)
Preliminary specification
SAA5281
CHARACTER SETS
The WST specification allows the selection of national
character sets via the page header transmission bits,
C12 to C14. The basic 96 character sets differ only in
13 national option characters as indicated in the
Tables 21, 22 and 23 with reference to their table position
in the basic character matrix illustrated in Table 20.
The IVT1.8* automatically decodes transmission bits
C12 to C14. Tables 14, 15 and 16 illustrate the character
matrixes.
Character bytes are listed as transmitted from b1 to b7.
Meshing
This is an alternative method of displaying teletext
subtitles, or similar boxed text superimposed on the TV
picture and operates by showing reduced contrast TV
pictures in place of the (black) background within the
boxed area. The Meshing effect is produced by toggling
the BLAN signal from IVT at pixel rate. By starting at the
same point each field, and toggling the start position each
line, a chequered pattern will result. This allows movement
to be seen behind the text information. The MESH
OFF/ON bit in Register 13 D5 controls this function.
Normally at zero, compatibility with IVT1.0 is maintained.
handbook, full pagewidth
MLA663
alphanumerics and
graphics 'space'
character
0000010
alphanumerics
character
1011010
alphanumerics or
blast-through
alphanumerics
character
0001001
alphanumerics
character
1111111
contiguous
graphics character
0110111
separated
graphics character
0110111
separated
graphics character
1111111
background
= _colour
contiguous
graphics character
1111111
=
display
colour
Fig.14 Character format.
1996 Nov 04
27