Z86129 Datasheet, PDF (31/50 Pages) Zilog, Inc. – NTSC LINE 21 DECIDER

PRELIMINARY
Z86129/130/131
NTSC Line 21 Decoder
Caption Activity Register Address = 08h
CAUTION: When XDS data recovery is enabled, the
external controller should never perform any other read
Bit D₇ D₆ D₅ D₄ D₃ D₂ D₁ D₀
1 ^{operation, except SS reads, in the beginning of field 2. This}
is most easily accomplished by using the end of field
T4
T3 T2
T1 CC4 CC3 CC2 CC1
(EOF) or data line end (DLE) interrupt to locate the end of
R RR
RR
RR R
field 2 or the vertical blanking interval (VBI) of field 1, and
then perform the READ SELECT and READ functions
during this portion of the video frame. Commands other
Figure 27. Caption Activity Register (Address = 08h) _{than READ SELECTS will not interfere with XDS data}
recovery regardless of their position in the video frame.
D₀-D₇-Activity Bits. Activity bits for Line 21 data channels
CC1-T4. Each bit will be set High when a mode setting Some examples of Z86129/130/131 WRITE commands
command for its data channel has been received on Line that could be used to set the XDS Filter Register are
21. The bit will be cleared to the Low state if no activity is shown below. The XDS Filter Register bit assignments are
detected in that data channel during the next 12-16 defined in the Z86129 Internal Register section of this
seconds or if there is a loss of lock.
specification.
XDS Data Recovery
The Z86129/130/131 is able to recover Extended Data
Services (XDS) information from the input video signal.
This data, formatted according to EIA-608, can contain a
wide variety of information about current and future
programs, the channel currently tuned, other channels and
miscellaneous data including time of day.
XDS data is only present in the even field. The
Z86129/130/131 can recover XDS data even while
performing its normal caption decoder or OSD functions.
XDS data packets are tagged according to a Class/Type
system defined by EIA-608. The Z86129/130/131 can be
programmed to filter the XDS data stream to extract only
the classes of interest to the application. An additional
level of filtering is provided that permits selection of certain
groups of packets that are of use in specific applications.
XDS filtering reduces the traffic on the serial bus, reduces
the load of the TV/VCR control processor and simplifies
external XDS decoding.
XDS data recovery is enabled by selecting one or more
classes in the XDS Filter register. Optionally, a secondary
filter code can be specified which further limits the packets
to be recovered. Once XDS recovery is enabled filtered
data pairs will be loaded into the serial output registers of
the Z86129/130/131 immediately upon receipt and in the
order received. The DAV and RD2 bits of the Serial Status
(SS) register will then go High, indicating the availability of
two output bytes. The external TV control processor does
not need to send a READ SELECT command in order to
read these data bytes.
When the XDS Filter register is set to 00h (the default
state) XDS recovery is disabled.
Table 14. XDS Data Extraction -
Example Filter Settings
{Write CMD,
Filter Code}
XDS Filter Output
{C5,41}
All In Band, Current Class packets
recovered.
{C5,61}
{C5,1F}
Program Rating, Current Class packets
recovered
Note: This Filter May be Used for V-CHIP
Data Packet Recovery (Z86129 and Z86130
only).
All XDS packets recovered.
{C5,01} All Current Class packets recovered.
{C5,28}
{C5,9F}
Time information recovered. This Filter
will extract the Time of Day (TOD) and
Local Time Zone (LTZ) packets from the
Miscellaneous Class data.
Note: This Filter May be Used to implement
Auto Clock-Setting in TVs, and VCRs
VCR Information recovered. Will select
TOD, LTZ, Net ID, Local Call Letters,
Impulse Capture, Tape Delay,
Composite 2 and Out of Band Channel
Number packets for recovery.
Filtered XDS Data Format
Filtered XDS data is output from the Z86129/130/131 in
the order it is received on Line 21. In other words, think of
the Z86129/130/131 XDS filter function as creating a new,
smaller stream of XDS data packets. This new data stream
will look exactly as though the Class and Type specified in
the XDS Filter Register (05h) are the only data encoded
on Line21 of field 2. The filtered data output from the
Z86129/130/131 will be in full compliance with EIA-608
specifications for XDS data streams; headers and control
codes intact. See Note paragraph below for a special
exception to this rule.
DS96TEL0200
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