
1995 Jun 15
23
Philips Semiconductors
Preliminary specification
Microcontrollers for TV tuning
control and OSD applications
PCA84C646; PCA84C846
11 CHARACTER ROM
Each character font is stored in the on-chip character ROM
in a 12
 ×
 19 dot matrix. However, only elements in Rows 1
to 18 (12
 ×
 18 dot matrix) can be selected as visible dots
on the screen.
Row 0 is only used for the combination of two characters
in a vertical direction when North-west shadowing mode is
selected (for details see Section 12.4). Row 0 contains the
same bit pattern of Row 18 of the character above it. If no
combined character in vertical direction is intended for this
character, Row 0 should be filled with all zeros.
11.1
Character ROM organization
ROM is divided into two parts: ROM1 and ROM2. The
organization of the bit patterns stored in ROM1 and ROM2
and the file format to submit to Philips for customized
character sets is shown in Fig.17.
A software package (OSDGEM) that assists in the design
of character fonts on-screen and that also automatically
generates the bit pattern HEX files is available on request.
The package is run under the MS-DOS environment for
IBM compatible PCs.
Regarding Fig.17 the following points should be noted.
1.
Row 0 of each font is reserved for vertical combination
of two fonts.
Binary 1 denotes visual dots.
ROM1 and ROM2 data files are in INTEL hex format
on a byte basis. Each byte is structured High nibble
followed by Low nibble.
The unused last byte of each font in ROM1 must be
filled with FFH.
The unused last 2
1
2
bytes in ROM2 must be filled with
the same data as held in the corresponding address in
ROM1.
The data bytes of the last 2 reserved fonts (Carriage
Return and Space Codes) should be filled with 00H.
CS denotes Checksum.
2.
3.
4.
5.
6.
7.
handbook, full pagewidth
11 10  9   8   7   6   5   4   3   2   1   0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Column
ROW
L
M
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
ROM2
ROM1
0 0 0
3 F C
2 2 0
2 2 0
3 F C
2 2 0
2 2 0
3 F C
2 2 0
2 2 0
3 F F 
0 0 1
0 0 1
5 5 3
5 5 2
0 0 6
0 0 C
0 5 8
0 3 0
0  0  0
2  2  0
3  F  C
2  2  0
2  2  0
3  F  F 
0  0  1
5  5  2
0  0  C
0  3  0
ROM1
ROM2
3  F  C
2  2  0
3  F  C
2  2  0
0  0  1 
5  5  3
0  0  6
0  5  8
ROM1
: 1 0 0 0 0 0 0 0 00  00  22  FC  03  22  20   F2  3F  01  20  55  0C  00     03
: 1 0 0 0 1 0 0 0  < - - -              DATA  FOR  FONT 2               - - -   12     34>
: 1 0 0 0 2 0 0 0  < - - -              DATA  FOR  FONT 3               - - -   56     78>
byte  #
0    1    2    3    4     5    6    7    8    9    A    B    C    D      E       F
F F 
F F 
F F 
ROM2
: 1 0 0 0 0 0 0 0  FC  03  22  20  C2  3F  20  12  00  53  65  00  58
: 1 0 0 0 1 0 0 0  < - - -              DATA  FOR  FONT 2            - - - >
: 1 0 0 0 2 0 0 0  < - - -              DATA  FOR  FONT 3            - - - >   5 X   78     FF 
  0 0   03     FF 
>
>
  1 X   34     FF 
>
2  2  0
CS
CS
CS
CS
CS
CS
MLB760
Fig.17  Font pattern stored in character ROM1 and ROM2.