GS2971A Datasheet, PDF (29/152 Pages) Gennum Corporation – Integrated audio clock generator

4. Detailed Description
4.1 Functional Overview
The GS2971A is a multi-rate SDI integrated Receiver which includes complete SMPTE
processing, as per SMPTE 425M, 292M and SMPTE 259M-C. The SMPTE processing
features can be bypassed to support signals with other coding schemes.
The GS2971A integrates Gennum's adaptive cable equalizer technology, achieving
unprecedented cable lengths and jitter tolerance. It features DC restoration to
compensate for the DC content of SMPTE pathological signals.
The device features an Integrated Reclocker with an internal VCO and a wide Input
Jitter Tolerance (IJT) of 0.7UI.
A serial digital loop through output is provided, which can be configured to output
either reclocked or non-reclocked serial digital data. The Serial Digital Output can be
connected to an external Cable Driver.
The device operates in one of four basic modes: SMPTE mode, DVB-ASI mode,
Data-Through mode or Standby mode.
In SMPTE mode, the GS2971A performs SMPTE de-scrambling and NRZI to NRZ
decoding and word alignment. Line-based CRC errors, line number errors, TRS errors
and ancillary data check sum errors can all be detected. The GS2971A also provides
ancillary data extraction. The entire ancillary data packet is extracted, and written to
host-accessible registers. Other processing functions include H:V:F timing extraction,
Luma and Chroma ancillary data indication, video standard detection, and SMPTE 352M
packet detection and decoding. All of the processing features are optional, and may be
enabled or disabled via the Host Interface.
Both SMPTE 425M Level A and Level B inputs are supported. The GS2971A also provides
user-selectable conversion from Level B to Level A for 1080p 50/60 4:2:2 10-bit formats
only.
In DVB-ASI mode, 8b/10b decoding is applied to the received data stream.
In Data-Through mode, all forms of SMPTE and DVB-ASI decoding are disabled, and the
device can be used as a simple serial to parallel converter.
The device can also be placed in a lower power Standby mode. In this mode, no signal
processing is carried out and the parallel output is held static. Placing the Receiver in
Standby mode will automatically place the integrated equalizer in power down mode as
well.
Parallel data outputs are provided in 20-bit or 10-bit multiplexed format for 3Gb/s, HD
and SD video rates. For 1080p 50/60 4:2:2 10-bit, the parallel data is output on the 20-bit
parallel bus as Y on 10 bits and Cb/Cr on the other 10 bits. As such, this parallel bus can
interface directly with video processor ICs. For other SMPTE 425M mapping structures,
the video data is mapped to a 20-bit virtual interface as described in SMPTE 425M. In all
cases this 20-bit parallel bus can be multiplexed onto 10 bits for a low pin count interface
with downstream devices. The associated Parallel Clock input signal operates at 148.5
or 148.5/1.001MHz (for all 3Gb/s HD 10-bit multiplexed modes), 74.25 or
74.25/1.001MHz (for HD 20-bit mode), 27MHz (for SD 10-bit mode) and 13.5MHz (for SD
20-bit mode).
GS2971A 3Gb/s, HD, SD SDI Receiver
Data Sheet
54311 - 2
September 2012
29 of 152