Z86129 Datasheet, PDF (16/50 Pages) Zilog, Inc. – NTSC LINE 21 DECIDER

Z86129/130/131
NTSC Line 21 Decoder
PRELIMINARY
Display Erase and Autoblanking
(Z86129 only)
The display is erased in the TEXT mode by the Start Text
command (but the box is maintained) and in the CAPTION
mode by the Erase Displayed Memory (EDM) command.
The non-displayed memory can be erased by the Erase
Non-displayed Memory (ENM) command.
Four other events can also cause the display to be erased.
1. A change in the display mode, such as from CC1 to
T1, CC1 to XDSF, and so forth, will clear the memory
and hence the display.
2. A loss of video lock, such as on a channel change, will
cause the screen to be cleared. The current active
display mode will not be changed. For example if CC1
was selected and ON before the channel change the
device will remain in the CC1/ON state after channel
change.
3. The third action that will clear the displayed memory is
when the autoblanking circuit is activated. The
autoblanking circuit monitors the presence of a Line 21
waveform in the video field corresponding to the data
channel selected for display. The decoder is held in
the Decoder OFF (TV) state until a Line 21 waveform
is continuously detected for a period of 0.5 seconds.
Once a valid Line 21 waveform has been detected for
0.5 seconds, and assuming that the user has selected
the Decoder ON state, the normal display for the data
channel selected will be presented. The autoblanking
circuit will be not activate again until a valid Line 21
waveform has been lost for 1.5 seconds. Any data
received during the 1.5 second period will reset the
counter so that autoblanking will only be activated on
continuous loss of the Line 21 waveform for 1.5
seconds. Note: Valid Line 21 waveform is defined as
the presence of a 7-cycle run-in clock and a start bit on
Line 21 of the field being examined.
4. The fourth method of clearing the screen is by the
action of the 16 Second Erase Timer. This function is
only active when a CAPTION or XDS display mode
has been selected. If no data is received for the
display channel selected for a 16 second period, the
on-screen memory will be erased. The decoder will
still be in the selected channel and with the decoder
ON, so that when data for the selected channels
resumes, it will be displayed.
Z86129/130/131 FEATURE SET
The primary features of the Z86129/130/131 are briefly
described below. More complete descriptions can be
found in later sections of this document.
VBI Data Processing
The Z86129/130/131 extracts the data in Line 21 of the
incoming video. All data channels, in both video fields are
supported. Specifically, the Z86129 can:
s Process data from both fields of Line 21
simultaneously.
s Output XDS data through the serial port while
displaying selected data.
s Output XDS data through the serial port raw or filtered.
s XDS filters are selectable from a list of pre-
programmed values including Program Rating and
Time of Day/Local Time.
s NTSC or PAL operation selectable.
The data extracted from Line 21 of the incoming video by
the Z86129 may be displayed in different ways according
to the user selection and the type of data. The display
features available on the Z86129 only are:
s Ten different Line 21 data display modes; CC1-CC4,
T1-T4, plus two standard templates for XDS displays.
s Pop-on, Paint-on and Roll-up CAPTION displays.
s TEXT display default is a full screen, 15 row display.
s User can vertically reduce and reposition the TEXT
display as desired.
s Color or Monochrome display mode selectable.
s XDSG Display Mode (channel grazing): automatic
display of Network Name, Call Letters, Program
Name, Program Length, and Time In Show data
packets.
s XDSF Display Mode (full information): automatic
display of XDSG Display Mode information plus:
Program Type (only basic types), and Program
Description.
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