MSP3402G Просмотр технического описания (PDF) - Micronas

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MSP3402G

Multistandard Sound Processor Family with Dolby Surround Pro Logic

Micronas 

MSP 34x2G

PRELIMINARY DATA SHEET

2.2.3. Preprocessing of Demodulator Signals

The NICAM signals must be processed by a deempha-

sis filter and adjusted in level. The analog demodu-

lated signals must be processed by a deemphasis fil-

ter, adjusted in level, and dematrixed. The correct

deemphasis filters are already selected by setting the

standard in the STANDARD SELECT register. The

level adjustment has to be done by means of the FM/

AM and NICAM prescale registers. The necessary

dematrix function depends on the selected sound

standard and the actual broadcasted sound mode

(mono, stereo, or bilingual). It can be manually set by

the FM Matrix Mode register or automatically set by

the Automatic Sound Selection.

2.2.4. Automatic Sound Select

In the Automatic Sound Select mode, the dematrix

function is automatically selected based on the identifi-

cation information in the STATUS register. No I2C inter-

action is necessary when the broadcasted sound

mode changes (e.g. from mono to stereo).

The demodulator supports the identification check by

switching between mono compatible standards (stan-

dards that have the same FM mono carrier) automati-

cally and non-audible. If B/G-FM or B/G-NICAM is

selected, the MSP will switch between these stan-

dards. The same action is performed for the standards:

D/K1-FM, D/K2-FM, D/K3-FM and D/K-NICAM.

Switching is only done in the absence of any stereo or

bilingual identification. If identification is found, the

MSP keeps the detected standard.

In case of high bit-error rates, the MSP 34x2G auto-

matically falls back from digital NICAM sound to ana-

log FM or AM mono.

Table 2–1 summarizes all actions that take place when

Automatic Sound Select is switched on.

To provide more flexibility, the Automatic Sound Select

block prepares four different source channels of

demodulated sound (see Fig. 2–4). By choosing one of

the four demodulator channels, the preferred sound

mode can be selected for each of the output channels

(loudspeaker, headphone, etc.). This is done by means

of the Source Select registers.

The following source channels of demodulated sound

are defined:

– “FM/AM” channel: Analog mono sound, stereo if

available. In case of NICAM, analog mono only

(FM or AM mono).

– “Stereo or A/B” channel: Analog or digital mono

sound, stereo if available. In case of bilingual broad-

cast, it contains both languages A (left) and B

(right).

– “Stereo or A” channel: Analog or digital mono

sound, stereo if available. In case of bilingual broad-

cast, it contains language A (on left and right).

– “Stereo or B” channel: Analog or digital mono

sound, stereo if available. In case of bilingual broad-

cast, it contains language B (on left and right).

Fig. 2–4 and Table 2–2 show the source channel

assignment of the demodulated signals in case of

Automatic Sound Select mode for all sound standards.

Note: The analog primary input channel contains the

signal of the mono FM/AM carrier or the L+R signal of

the MPX carrier. The secondary input channel con-

tains the signal of the second FM carrier, the L−R sig-

nal of the MPX carrier, or the SAP signal.

primary

channel

FM/AM

secondary

channel

Prescale

NICAM A

NICAM

NICAM

Prescale

FM/AM 0

Automatic Stereo or A/B 1

Sound

Select

Stereo or A 3

Stereo or B 4

LS Ch.

Matrix

Output-Ch.

Matrices must

be set once to

stereo

SC2 Ch.

Matrix

Fig. 2–4: Source channel assignment of demodulated

signals in Automatic Sound Select Mode

2.2.5. Manual Mode

Fig. 2–5 shows the source channel assignment of

demodulated signals in case of manual mode. If man-

ual mode is required, more information can be found in

Section 6.7. “Demodulator Source Channels in Manual

Mode” on page 105.

primary

channel

FM/AM

secondary

channel

Prescale

NICAM A NICAM

NICAM

Prescale

FM-Matrix FM/AM 0

NICAM

(Stereo or A/B) 1

LS Ch.

Matrix

Output-Ch.

Matrices

must be set

according

the standard

SC2 Ch.

Matrix

Fig. 2–5: Source channel assignment of demodulated

signals in Manual Mode

12

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