STV82X8 datasheet(20/157 Pages) STMICROELECTRONICS

20 / 157 page

Digital Demodulator

STV82x8

20/157

must be reset by re-programming the LSB of register IRQ_STATUS while checking the detected

standard status by reading registers AUTOSTD_STATUS.

ITo 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

(Autostandard).

(1) L+R and L-R must not exceed 50 kHz

Sound Carrier Frequency Offset Recovery:IF Carrier frequency can be adjusted with register

CAROFFSET1 within a large range (up to 120 kHz ) while the Automatic Standard Recognition

System remains active. The frequency offset estimation is written in registers DEMOD_DC_LEVEL

and can be used to implement the Automatic Frequency Control (AFC) via an external I²2C control.

Manual Mode: If required, the Automatic Standard Recognition System system can be disabled

(Manual mode) and the user can control all registers including those only controlled by the

Automatic Standard Recognition System function when active. Manual mode is selected in register

AUTOSTD_CTRL by setting to 0 bits SAP_CHECK, STEREO_CHECK and MONO_CHECK.

Table 4: BTSC Standard

Source

Modulation

Frequency

Range

Audio Pre-

processing

Sub-Carrier

Modulation

Type

Sub-Carrier

Deviation

Aural

Carrier

(4.5 MHz)

Peak

Deviation

Monophonic

L+R

0.05 -15 kHz

75 µs Pre-

emphasis

25 kHz (1)

Pilot

0Fh

5 kHz

Stereophonic

L-R

0.05 -15 kHz

DBX

Compression

2Fh

AM DSB SC

50 kHz(1)

SAP

2nd Channel

0.05 -15 kHz

DBX

Compression

5Fh

10 kHz

15 kHz

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