LMH0031 Datasheet, PDF (33/39 Pages) National Semiconductor (TI) – SMPTE 292M/259M Digital Video Deserializer Descrambler with Video and Ancillary Data FIFOs

LMH0031
www.ti.com
SNLS218A – JANUARY 2006 – REVISED APRIL 2013
PROCESSING NON-SUPPORTED RASTER FORMATS
The number and type of HD raster formats has proliferated since the LMH0031 was designed. Though not
specifically capable of fully or automatically processing these new formats, the LMH0031 may still be capable of
deserializing them. The user is encouraged to experiment with processing these formats, keeping in mind that
the LMH0031 has not been tested to handle formats other than those detailed in Table 4. Therefore, the results
from attempts to process non-supported formats is not ensured. The following guidelines concerning device
setup are provided to aid the user in configuring the LMH0031 to attempt limited processing of these other raster
formats.
In general, the device is configured to defeat its automatic format detection function and to limit operation to a
general HD format. (The user should consult Table 4 for guidance on the format groups similar to the non-
supported one to be processed). Since most non-supported formats are in the HD group, the LMH0031 should
be configured to operate in HD-ONLY mode by setting bit-5 of the FORMAT 0 register (address 0Bh). Also, the
device should be further configured by loading the FORMAT SET[4:0] bits of this register with the general HD
sub-format code. In addition, since control data is being written to the port, AD[9:8] must be driven as 11b. The
complete data word for this general HD sub-format code with HD-ONLY bit set is 33Fh. Since this format differs
from those in the table, the EAV/SAV indicators are disabled. Without these indicators, line numbering and CRC
processing are disabled and ANC data extraction will not function. Output video chroma and luma data will be
word-aligned. Post-processing of the parallel data output from the LMH0031 will be needed to implement CRC
checking or line number tracking.
USING EXTERNAL VCXO FOR VCLK
The EXTERNAL V_CLK bit of VIDEO CONTROL 0 (register address 55h) is a special application function which
enables use of an external VCXO as a substitute for the internally generated V_CLK. Additional circuitry is enabled
within the LMH0031 which provides phase-frequency detection and control voltage output for the VCXO. An
external loop filter and voltage amplifier are required to interface the control voltage output to the VCXO
frequency control input. When this function is used, the R_BB output function is changed from the bias supply
output to the control voltage output of the phase-frequency detector. The V_CLK output changes function,
becoming the input for the VCXO signal.
Figure 8 shows an example using dual VCXOs for V_CLK to handle both standard and high definition video.
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