LMH0031 Datasheet, PDF (12/39 Pages) National Semiconductor (TI) – SMPTE 292M/259M Digital Video Deserializer Descrambler with Video and Ancillary Data FIFOs

LMH0031
SNLS218A – JANUARY 2006 – REVISED APRIL 2013
1 PF
82.5:
825:
LMH0031
SDI
1 PF
SDI
82.5:
825:
1 nF
8.66 k:
4.75 k:
R_BB
R_REF
www.ti.com
Figure 2. Optional Input Biasing Scheme
The SMPTE descrambler receives NRZI serial data, converts it to NRZ, then decodes it to either 10-bit standard
definition or 20-bit high definition parallel video data using the reverse polynomial X⁹ + X⁴ + 1 as specified in the
respective standard: SMPTE 259M, SMPTE 344M (proposed) or SMPTE 292M. The data reception bit order is
LSB-first. All data processing is done at the parallel rate.
The LMH0031 incorporates circuitry that implements a method for handling data that has been subjected to LSB
dithering. When so enabled, data from the de-scrambler is routed for de-dithering. The De-Dither Enable bit in
the VIDEO INFO 0 control register enables this function. De-dithering of data present in the vertical blanking
interval can be selectively enabled by use of the V De-Dither Enable bit in the VIDEO INFO 0 control register.
The initial condition of De-Dither Enable and V De-Dither Enable is OFF.
The descrambler supplies signals to theTRS character detector which identifies the presence of the valid video
data. The TRS character detector processes the timing reference signals which control raster framing. TRS
(sync) characters are detected and the video is aligned on word boundaries. Data is re-synchronized with the
parallel word-rate clock. Interraction and operation of the character alignment control signals and indicators
Framing Mode, Framing Enable and NSP (New Sync Position) is described later in this datasheet.
The LMH0031 implements TRS character LSB-clipping as prescribed in ITU-R BT.601. LSB-clipping causes all
TRS characters with a value between 000h and 003h to be forced to 000h and all TRS characters with a value
between 3FCh and 3FFh to be forced to 3FFh. Clipping is done after descrambling and de-dithering.
12
Submit Documentation Feedback
Product Folder Links: LMH0031
Copyright © 2006–2013, Texas Instruments Incorporated