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2000 Feb 23
50
Philips Semiconductors
Preliminary specification
TV microcontrollers with Closed Captioning (CC)
and On-Screen Display (OSD)
SAA55xx
18.4
Character and attribute coding
This section describes the character and attribute coding
for each mode.
18.4.1
CC
MODE
Character coding is split into character oriented attributes
(parallel) and character group coding (serial). The serial
attributes take effect either at the position of the attribute
(set at), or at the following location (set after) and remain
effective until either modified by a new serial attribute or
until the end of the row. A serial attribute is represented as
a space (the space character itself however is not used for
this purpose), the attributes that are still active,
e.g. overlineandunderlinewillbevisibleduringthedisplay
of the space.
The default setting at the start of a row is:
×1
size
Flash off
Overline off
Underline off
Italics off
Display mode = superimpose
Fringing off
Background colour duration = 0
End of row = 0.
The coding is done in 12-bit words. The codes are stored
sequentially in the Display memory. A maximum of
768 character positions can be defined for a single display.
Table 15
Parallel character coding
18.4.2
TXT
MODE
Character coding is in a serial format, with only one
attribute being changed at any single location. The serial
attributes take effect either at the position of the attribute
(set at), or at the following location (set after). The attribute
remains effective until either modified by new serial
attributes or until the end of the row.
The default settings at the start of a row are:
Foreground colour white (CLUT address 7)
Background colour black (CLUT address 8)
Horizontal size
×
1, vertical size
×
1 (normal size)
Alphanumeric on
Contiguous mosaic graphics
Release mosaics
Flash off
Box off
Conceal off
Twist off.
The attributes have individual codes which are defined in
the basic character table (see Fig.22).
BITS
DESCRIPTION
0 to 7
8 to 10
11
8 bit character code
3 bits for 8 foreground colours
mode bit: 0 = Parallel code