GS1559-CBE2 Gennum Corp., GS1559-CBE2 Datasheet - Page 34

• Manufacturer Part Number: GS1559-CBE2
• Description: HD-LINX II Multi-Rate Deserializer with Loop-Through Cable Driver
• Manufacturer: Gennum Corp.

4.7 SMPTE Functionality
4.7.1 SMPTE Descrambling and Word Alignment
4.7.2 Internal Flywheel
The GS1559 is said to be in SMPTE mode once the device has detected SMPTE
TRS sync words and locked to the input data stream as described in
The device will remain in SMPTE mode until such time that SMPTE TRS sync
words fail to be detected.
The lock detect block may also drop out of SMPTE mode under the following
conditions:
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•
•
•
TRS word detection is a continuous process and both 8-bit and 10-bit TRS words
will be identified by the device in both SD and HD modes.
In master mode, the GS1559 sets the SMPTE_BYPASS pin HIGH and the
DVB_ASI pin LOW to indicate that it has locked to a SMPTE input data stream.
When operating in slave mode, the application layer must assert the DVB_ASI pin
LOW and the SMPTE_BYPASS pin HIGH in order to enable SMPTE operation.
After serial-to-parallel conversion, the internal 10-bit or 20-bit data bus is fed to the
SMPTE descramble and word alignment block. The function of this block is to carry
out NRZI-to-NRZ decoding, descrambling according to SMPTE 259M or 292M,
and word alignment of the data to the TRS sync words.
Word alignment occurs when two consecutive valid TRS words (SAV and EAV
inclusive) with the same bit alignment have been detected.
In normal operation, re-synchronization of the word alignment process will only
take place when two consecutive identical TRS word positions have been
detected. When automatic or manual switch line lock handling is 'actioned', (see
Section
TRS code word.
The GS1559 has an internal flywheel which is used in the generation of internal /
external timing signals, in the detection and correction of certain error conditions
and in automatic video standards detection. It is only operational in SMPTE mode.
The flywheel consists of a number of counters and comparators operating at video
pixel and video line rates. These counters maintain information about the total line
length, active line length, total number of lines per field / frame, and total active
lines per field / frame for the received video stream.
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RESET_TRST is asserted LOW
CDx is HIGH
SMPTE_BYPASS is asserted LOW in slave mode
DVB_ASI is asserted HIGH in slave mode
4.7.3), word alignment re-synchronization will occur on the next received
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GS1559 Preliminary Data Sheet
November 2004
Section
34 of 74
4.6.1.