Z8623012SSG Datasheet, PDF (37/61 Pages) Zilog, Inc. – ADVANCED PROGRAM BLOCKING AND NTSC LINE 21 XDS DECODER

XDS DATA RECOVERY
CONTROL REGISTERS
The XDS filters on the Z86230 greatly reduce the amount of Field 2 data passed
on to the master device for further processing and interpretation; however, the
master device must still interpret the filtered data stream in accordance with EIA-
608A. In other words, only the selected XDS data Class and Type packets are cho-
sen. The filtered data stream contains all of the XDS command and data packets.
Though the Z86230 filtered data stream is in full compliance with the EIA-608
specification, the master device must still interpret the necessary packets to ensure
full compliance with EIA-608A.
NOTE: The Z86230 XDS filter for Program Rating information functions differently than
all other Z86230 predefined XDS filters. This change has been made to minimize the
amount of data passed through the Program Rating XDS filter, thereby minimizing the
interpretation and communications load on the master device. When the XDS Filter Regis-
ter is set to 61h (Class=01h (Current), Type=05h (Program Rating) the only data from
Line 21 Field 2 that passes through the filter is:
1. Program Rating Packet: [xxh,xxh]. The Current Class Program Rating
data byte pair as defined in EIA-608. The program’s rating is encoded per
EIA-608 in the xxh byte pair.
2. The END Packet [0Fh,CHKSUM]. A 2-byte packet that includes a CHKSUM
computed per EIA-608A. The checksum calculation includes the START
packet [01h,05h] even though this value was not passed through the filter.
PS000401-TVC0699
Z86230—PRELIMINARY
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