MSP3410B datasheet(25/68 Pages) MICRONAS

25 / 68 page

PRELIMINARY DATA SHEET

MSP 3410 B

ITT Semiconductors

LOAD_SEQ_1/2

Channel 1:

NICAM Parameter

NICAM_START

NICAM_READ

LOAD_SEQ_1

Channel 1:

FM2 Parameter

IDENT_CHECK

Pilot?

LOAD_SEQ_1

Channel 1:

NICAM Parameter

Fig. 11–3: CCU software flow diagram: Standard B/G

with NICAM or FM stereo

1) The first READ could result in incorrect values.

Yes

FM_

NICAM_CHECK

NICAM

START

NICAM_READ

Pause

Yes

Pause

Audio Processing Init

11.6.5. Automatic Search Function for FM-Carrier

Detection

The AM demodulation ability of the MSP 3410 B offers

the possibility to calculate the “field strength” of the mo-

mentarily selected FM carrier which can be read out by

the CCU. In SAT receivers this feature can be used to

realize an automatic FM carrier search.

Therefore, the MSP has to be switched to AM-mode

(Bit 8 of MODE_REG). The sound-IF frequency range

must now be “scanned” in the MSP-channel 2 by means

of the programmable quadrature mixer with an appropri-

ate incremental frequency (i.e. 10 kHz).

After each incrementation there is a field strength value

available at the DC level register FM1, which must be ex-

amined for relative maxima by the CCU. This results in

either continuing search or switching the MSP back to

FM demodulation mode.

During the search process the FIR_REG_2 must be

loaded with the coefficient set “AUTOSEARCH”, which

enables small bandwidth resulting in appropriate field

strength characteristics. The absolute field strength val-

ue (can be read out of “DC Level Readout FM1”) also

gives information on whether a main FM carrier or a sub-

carrier was detected, and as a practical consequence

the FM bandwidth (FIR_REG_1/2) and the deemphasis

(50

µs or adaptive) can be switched automatically. For

a detailed description of the automatic search function

please refer to the corresponding MUBI program.

11.6.6. Automatic Standard Detection

The AM demodulation ability of the MSP 3410 B enables

also a simple method to decide between standard B/G

(FM-carrier at 5.5 MHz) and standard I (FM-carrier at 6.0

MHz). It is achieved by tuning the MSP in the AM-mode

to the two discrete frequencies and evaluating the field

strength via the DC level register.

MSP3410B Datasheet(PDF) 25 Page - Micronas

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