STV8206 Datasheet, PDF (13/97 Pages) STMicroelectronics – Multistandard TV Audio Processor and Digital Sound Demodulator

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
register AUTO_CTRL) for the DK standard while the AUTOSTD system remains active. The
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
M/N
B/G
I
L
D/K
D/K1
D/K2
D/K3
FM Mono
FM 2 Carriers
FM Mono
FM/NICAM
FM 2 Carriers
FM Mono
FM/NICAM
AM Mono
AM/NICAM
FM Mono
FM/NICAM
FM 2 Carriers
FM 2 Carriers
FM 2 Carriers
Type
Name
Carrier 1 Carrier 2
(MHz) (MHz)
FM/AM Deviation
Min. Typ. Max.
Roll-
De-emphasis off
(%)
Pilot
Frequency
(kHz)
4.5
15
27
50
A2+
4.724
5.5
5.850
27
50
80
A2
5.742
6.0
27
50
80
6.552
0.5
1.0
5.850
6.5
5.850
6.258
27
50
80
A2*
6.742
5.742
75 µs
50 µs
J17
50 µs
50 µs
J17
55.069
40
54.6875
100
100
J17
40
50 µs
J17
40
50 µs
54.6875
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