STV8216 datasheet(13/97 Pages) STMICROELECTRONICS

13 / 97 page

13/97

STV82x6

Demodulator Block

Each mono and stereo standard can be removed (or added) from the List of Standards to be

recognized by programming registers AUTO_SCKM and AUTO_SCKST, respectively. The identified

standard is displayed in register AUTO_STAT and any change to standard is flagged to the host

system via pin IRQ. This flag must be reset by re-programming the MSBs of register AUTO_CTRL

while checking the detected standard status by reading registers AUTO_STAT, NICAM_STAT and

ZWT_STAT. Moreover, the detection of Stereo mode during demodulation is also flagged in register

AUTO_STAT and on output pin ST.

Important: L/L’ and D/K standards cannot be automatically processed because the same frequency

is used for the MONO carrier. An exclusive L/DK selection must programmed in register

AUTO_CTRL. This may be externally controlled by detecting the RF modulation sign, which is

negative for all TV standards except L/L’.

To recover out-of standard FM deviations or the Sound Carrier Frequency Offset, additional I²C

controls are provided without interfering with the Automatic Standard Recognition System

(AUTOSTD).

DK-NICAM Overmodulation Recovery: Four different FM deviation ranges can be selected (via

maximum FM deviation is 500 kHz in DK Mono mode and 350 kHz in DK NICAM mode (limited by

overlapping FM and NICAM spectrum values). The demodulated signal peak level (proportional to

the FM deviation) is detected by the Peak Detector and written to registers PEAK_DET_STATL and

PEAK_DET_STATR. This value is used to implement Automatic Overmodulation Detection via an

external I²C control.

Important: Only the selection of the 50 kHz FM deviation standard is compatible with the other DK-

A2* standards (DK1, DK2 or DK3). These standards must be removed from the list of standards

(registers AUTO_SCKM and AUTO_SCKST) when programming larger FM deviations reserved

only for DK-NICAM standards.

Table 3: Standards covered by the Automatic Standard Recognition System (AUTOSTD)

System

Sound Type

Type

Name

Carrier 1

(MHz)

Carrier 2

(MHz)

FM/AM Deviation

De-emphasis

Roll-

off

(%)

Pilot

Frequency

(kHz)

Min.

Typ.

Max.

M/N

FM Mono

4.5

75 µs

FM 2 Carriers

A2+

4.724

55.069

B/G

FM Mono

5.5

50 µs

FM/NICAM

5.850

J17

FM 2 Carriers

5.742

50 µs

54.6875

FM Mono

6.0

50 µs

100

FM/NICAM

6.552

J17

100

AM Mono

6.5

0.5

1.0

AM/NICAM

5.850

J17

D/K

FM Mono

50 µs

FM/NICAM

5.850

J17

D/K1

FM 2 Carriers

A2*

6.258

50 µs

54.6875

D/K2

FM 2 Carriers

6.742

D/K3

FM 2 Carriers

5.742

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