ST6391 Datasheet, PDF (48/68 Pages) STMicroelectronics – 8-BIT HCMOS MCUs FOR TV FREQUENCY SYNTHESIS WITH OSD

ST6391,92,93,95,97,99
ON-SCREEN DISPLAY (Continued)
Each line must begin with a format character which
describes the format of that line and of the first
word. This character is not displayed.
A space character defines the format of sub-
sequent words. A space character is denoted by a
one in bit 6 in the display RAM. If bit 6 of the display
RAM is a zero, the other six bits define one of the
64 display characters.
The colour, background and enable can be pro-
grammed by word. This information is encoded in
the space character between words or in the for-
mat character at the beginning of each line. Five
bits define the colour and background of the follow-
ing word, and determine whether it will be dis-
played or not.
Characters are stored in a 6 x 9 dot format. One dot
is defined vertically as 2H (horizontal lines) and
horizontally as 2/fosc if the smallest character size
is enabled. There is no space between characters
or lines if the vertical space enable (VSE) and hori-
zontal space enable (HSE) bits are both zero. This
allows the use of special graphics characters.
The normal alphanumeric character set is format-
ted to be 5 x 7 with one empty row at the top and
one at the bottom and one empty column at the
right. If VSE and HSE are both zero, then the spac-
ing between alphanumeric characters is 1 dot and
the spacing between lines ofalphanumericcharac-
ters is 2H.
The character size is programmed by line through
the use of the size bit (S) in the format character
and the global size bits (GS1 and GS2). The verti-
cal spacing enable bit (VSE) located in the format
character controls the spacing between lines. If
this bit is set to one, the spacing between lines is
defined by the vertical spacing register, otherwise
the spacing between lines is 0.
The spacing between words is controlled by the
horizontal space enable bit (HSE) located in the
space character. If this bit is set to one, the spacing
between words is defined by the horizontal spacing
register, otherwise the space character width of 6
dots is the spacing between words.
The formats for the display character, space
character and format character are described
hereafter.
Figure 56. Space Character Register
Explanation
Space Character Format
See Data RAM Table Description
for Specific Address
( Write Only)
D7 D6 D5 D4 D3 D2 D1 D0
HSE = Horizontal Space Enable
WE = Word Enable Bit
BGS = Backround Select
B = B Colour Bit
G = G Colour Bit
R = R Colour Bit
Fixed to “1”
Unuse d
D7. Not used.
D6. This pin is fixed to “1”.
R, G, B. Colour. The 3 colour control bits define the
colour of the following word as shown in Table be-
low.
Space Character Register Colour Setting.
R
G
B
Colour
0
0
0
Black
0
0
1
Blue
0
1
0
Green
0
1
1
Cyan
1
0
0
Red
1
0
1
Magenta
1
1
0
Yellow
1
1
1
White
BGS. Background Select. The background select
bit selects the desired background for thefollowing
word. There are two possible backgrounds defined
by the bits in the Background Control Register.
“0” -The background on the following word is en-
abled by BG0 and the colour is set by R0, G0,
and B0.
“1” -The background on the following word is en-
abled by BG1 and the colour is set by R1, G1,
and B1.
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