Z90251 Datasheet, PDF (41/97 Pages) Zilog, Inc. – eZVision 200 Television Controllers with OSD

Z90255 ROM and Z90251 OTP
32 KB Television Controller with OSD
33
Table 17 BGR Mesh Colors
B
G
R
Color
0
0
0
Black
0
0
1
Red
0
1
0
Green
0
1
1
Yellow
1
0
0
Blue
1
0
1
Magenta
1
1
0
Cyan
1
1
1
White
Bit 3,P20 for Halftone, selects mesh or halftone effect. If bit 3 is set to 1, P20
outputs halftone. If reset to 0,P20 is a normal I/O pin.
Bit 2, Software Field Number/Polarity of Halftone Output, has several possible
values. The value of this bit remains the same for the entire mesh window; it does
not change from row to row.
If bit 3 is set to 1 (halftone), bit 2 defines the polarity of halftone output. If bit 3 is
reset to 0 and bit 1 is set to 1, then bit 2 defines the field number (even or odd).
Bit 1, Software Mesh, defines whether hardware or software sets the current field
number. When the value equals 0, hardware defines field number. When the
value equals 1, software defines the field number.
Bit 0, Mesh Enable, disables or enables using mesh. This field is used in
conjunction with MR_EN (0). The value of Mesh Enable is changed only when
Mesh Window Row equals 0 (the current OSD row is not part of a mesh window). If
the value is changed when the current row is part of the mesh window, partial or
missing characters are likely to be displayed.
5.4 OSD Fade
Fading is the gradual disappearance of the OSD. Fading occurs vertically, up or
down. Figure 11 shows the fade-down effect.
Fade control registers can only be updated during V_SYNC, not during row interrupt.
Otherwise, unexpected results can occur.
PS001301-0800