GS9090 Data Sheet
3.7 DVB-ASI Functionality
The GS9090 enters DVB-ASI mode once the device has detected 32 consecutive
DVB-ASI words without a single word or disparity error being generated. The
device will remain in DVB-ASI mode until 32 consecutive DVB-ASI words or
disparity errors are detected, or until SMPTE TRS ID words have been detected.
The lock detect block may also drop out of DVB-ASI mode under the following
conditions:
•
•
•
RESET is asserted LOW
Both AUTO/MAN and DVB_ASI are asserted LOW
LOCKED pin is LOW (i.e. the device loses lock to the input signal)
K28.5 sync patterns in the received DVB-ASI data stream will be detected by the
device in either inverted or non-inverted form.
In Auto mode, the GS9090 sets the SMPTE_BYPASS pin LOW and the DVB_ASI
pin HIGH to indicate that it has locked to a DVB-ASI input data stream. When
operating in Manual mode, the application layer must set the DVB_ASI pin HIGH
to enable DVB-ASI operation. The SMPTE_BYPASS pin will be ignored.
3.7.1 DVB-ASI 8b/10b Decoding
After serial-to-parallel conversion, the internal 10-bit data bus is fed to the DVB-ASI
8b/10b decode and word alignment block. The function of this block is to word align
the data to the K28.5 sync characters, and 8b/10b decode and bit-swap the data
to achieve bit alignment with the data outputs.
The extracted 8-bit data will be presented to DOUT [7:0], bypassing all internal
SMPTE mode data processing.
3.7.2 Status Signal Outputs
In DVB-ASI mode, the DOUT9 and DOUT8 pins will be configured as DVB-ASI
status signals WORDERR and SYNCOUT respectively.
SYNCOUT will be HIGH whenever a K28.5 sync character is present on the output.
WORDERR will be HIGH whenever the device has detected an illegal code word
or there is a running disparity error.
3.8 Data-Through functionality
The GS9090 may be configured by the application layer to operate as a simple
serial-to-parallel converter. In this mode, the device presents data to the output
data bus without performing any decoding, descrambling, or word-alignment.
Data-Through functionality is enabled only when the application layer sets the
AUTO/MAN, SMPTE_BYPASS, and DVB_ASI input pins LOW. Under these
conditions, the lock detect block allows 270Mb/s input data not conforming to
SMPTE or DVB-ASI streams to be reclocked and deserialized. If the device is in
28201 - 1 July 2005
29 of 70
GENNUM [ GENNUM CORPORATION ]
