L64780 LSI Logic Corporation, L64780 Datasheet - Page 32

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

2.9 Mode Control Logic
2-14
If previously stored mode data are available, they are used when a
channel is selected or when the signal strength rises after a period of
signal loss. This is done by the means of an external microprocessor and
makes acquisition faster. When the Mode Control Logic becomes an
error-free TPS block, mode data from that TPS block replaces any
previously determined mode data.
In this context, the mode data consists of:
The mode control logic configures all the demodulator blocks whose
operation is affected by these parameters. Acquisition of the demodulator
is outlined in the following steps:
1. Achieve full synchronization of the FFT start and the clock frequency.
2. Make coarse and fine automatic frequency control (AFC) corrections,
3. Equalize the channel frequency response, once the Symbol Number
4. Wait up to one frame for the start of a TPS block, and wait another
5. The modulation system, hierarchy information, and code rate from
Architectural Overview
2 k or 8 k mode
Length of the guard interval
Modulation system
Hierarchy information
Inner code rate
and achieve frequency synchronization.
is zero.
frame for the complete TPS block to be received. There is a wait of
one or more additional frames, if necessary, until a TPS block is
received without errors.
the TPS data are used to configure the Viterbi metric assignment
block, and, by means of the microprocessor interface, the external
Viterbi decoder(s).