L64780 LSI Logic Corporation, L64780 Datasheet - Page 31

• Manufacturer Part Number: L64780
• Description: Dvb-t Cofdm Demodulator Technical Manual 2/00
• Manufacturer: LSI Logic Corporation

2.8 TPS Decoding and Frame Synchronization
The R and C values for the low-pass filter must meet the requirement
shown in
Equation 2.16
This block takes the sequence of complex numbers from the output of
the FFT block and recovers the Transmission Parameter Signalling (TPS)
data defined in paragraph 4.6 of the DVB-T/ETSI specification. The block
passes the resulting data to the control logic of the L64780; it thus
configures the mode of operation of much of the demodulator’s circuitry.
The TPS data contains information on:
The guard interval and mode interaction cannot be used for acquisition,
but assist the receiver in handling a reconfiguration of the transmission.
By implication, the TPS also indicates the phase of the four-symbol
sequence of insertion of scattered pilots.
The TPS Decoder extracts the data bits from the TPS carriers and
retains the most recent 67 bits. The decoder detects the start of the
frame and carries out the Bose-Chaudhuri-Hocque (BCH) error check on
the block of 67 bits, so that data containing errors can be discarded. All
the data in the list above are passed to the control logic along with two
flags: one indicates the start of a frame; the other indicates whether the
error check detects errors. If there were no errors, the control logic uses
the data to configure the demodulator, discarding any previous settings.
The settings can be read and initialized through the microprocessor
interface, which allows previously stored settings to be used when a
channel is selected, making acquisition faster.
TPS Decoding and Frame Synchronization
The modulation system
Whether the transmission is hierarchical
What the value of
The inner code rate(s)
The guard interval
The mode: 2 k or 8 k
Equation
R
AFC
2.16:
C
AFC
is (if the transmission is hierarchical)
=
330 s
2-13