GS9060 Data Sheet
3.7 SMPTE Functionality
The GS9060 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 Section 3.6
on page 28. 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:
•
•
•
•
RESET_TRST is asserted LOW
CDx is HIGH
SMPTE_BYPASS is asserted LOW
DVB_ASI is asserted HIGH
TRS word detection is a continuous process and both 8-bit and 10-bit TRS words
will be identified by the device.
The application layer must assert the DVB_ASI pin LOW and the
SMPTE_BYPASS pin HIGH in order to enable SMPTE operation.
3.7.1 SMPTE Descrambling and Word Alignment
After serial-to-parallel conversion, the internal 10-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, 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',
Section 3.7.3 on page 31, word alignment re-synchronization will occur on the next
received TRS code word.
3.7.2 Internal Flywheel
The GS9060 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.
The flywheel 'learns' the video standard by timing the horizontal and vertical
reference information contained in the TRS ID words of the received video stream.
Full synchronization of the flywheel to the received video standard therefore
requires one complete video frame.
22208 - 8 January 2007
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