z86131 ZiLOG Semiconductor, z86131 Datasheet - Page 43

• Manufacturer Part Number: z86131
• Description: Ntsc Line 21 Decoder
• Manufacturer: ZiLOG Semiconductor

ZiLOG
ON-SCREEN DISPLAY (Z86129 Only)
OSD Operation
The Z86129 has a fully programmable, general purpose
OSD built in. The user can supply information for display
through the serial port. In addition to all the normal and ex-
tended features of the VBI data display modes, OSD mode
also has available added graphics characters, Double-High
and Double-Wide characters and the ability to position the
display anywhere on the screen with an adjustable (vertical)
box size. The Double-High and double-wide characters are
especially useful for creating OSD screens for display in-
side a Picture-in-Picture (PiP) window. The OSD display
mode can use either 13 or 15 lines per row, with box or drop
shadow. The default is 15 scan lines per row and drop shad-
ow. Enhanced attributes are always enabled.
The 15 scan line per row display can only display 13 rows
on-screen when in the NTSC mode. Rows 14 and 15 is off-
screen and should not be addressed. In the PAL mode all
rows are visible.
The 15 scan lines per row mode display can display the full
graphic characters and accented capital letters and descend-
ers without the potential overlap that would result from the
13 scan line per row display. If the OSD display mode is
changed to a 13 scan line per row mode, the top two scan
lines of any graphics or accented capital letter is “ORed”
together with the bottom two scan lines from the row above.
In 13 line-drop shadow mode, the result is a side-shadow
effect. Graphics characters should not be used in the 13 line-
drop shadow mode.
OSD Character Set
There are 256 possible addresses in the OSD character set.
Figure 38 illustrates the address map in the range 00h–BFh.
This portion of the addressable space contains the control
DS007200-TVX0199
P R E L I M I N A R Y
bytes and regular character set. The address map in the
range C0h–FFh is illustrated in Figure 20.
These addresses are shared by the Extended Character set
and the Graphics Character set. Any particular OSD screen
can use one or the other of these sets of characters but not
both.
The character set in force is controlled by the type of display
mode being invoked. When Drop Shadow is being used, by
default, the Graphics Character set is displayed in response
to an address in the C0h–FFh range. However, if a BOX
display is used, the Extended Character set is invoked. In
either case the user can switch to the other set by means of
the appropriate command, GRAPHICS or EXTENDED.
The V
from the TV receiver when V Lock = V
This mode permits an OSD display even when no video in-
put is present. If this mode is not required, the default state
V Lock = VIDEO should be active and this pin then carries
the INTRO output signal.
OSD Commands
OSD commands are one and two byte commands. They are
used to control the loading of data for OSD display and their
presentation to the screen. Normally OSD display mode
uses 15 TV lines per display row to enhance the OSD pre-
sentation.
The two byte commands enable direct access to any location
on the display screen. The user may construct displays of his
own choosing by using these commands. Each command
byte pair consists of an instruction byte followed by a data
byte (see the Sample Z86129 OSD Program on page 45).
IN
/INTRO pin serves as the input for a Vertical Pulse
NTSC Line 21 Decoder
IN
Z86129/130/131
mode is enabled.
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