STV8203 ST Microelectronics, STV8203 Datasheet - Page 20

• Manufacturer Part Number: STV8203
• Description: MULTISTANDARD TV SOUND DEMODULATOR
• Manufacturer: ST Microelectronics

STV8203
PROGRAMMING THE DEVICE (continued)
AO-CONTROL (AUTOSTANDARD Control)
Address
Type
Reset
AUTOSTANDARD controls the audio matrix when the user has selected the DAC as source (AUD-MX-
CNT bits[6:4] = 010). In this case it will mute the outputs or select MIN. These functions can be overriden
by bits 6 and 7 below.
MUTE OV
MONO OV
UNMUTE
C4 OV
STANDARD
CHECK
AO-TIMEOUT (AUTOSTANDARD Timer Adjustment)
Address
Type
Reset
Time 1 is used for NICAM and FM mono validation and time 2 for Zweiton. If the standard is not found
within this time limit, the next standard will be tried. Time 1 = decimal [bit 3:0] x 32ms. Time 2 = deci-
mal [bit 7:4] x 128ms. Time 1 default value is 160ms. Time 2 default value is 1280ms.
A time of 0ms should not be programmed.
20/31
MUTE OV
bit 7
bit 7
: 0E
: R/W
: 0001 1111
: Mute override, 1 = mute (override AUTOSTANDARD)
: FM/AM Mono override, 1 = mono (override AUTOSTANDARD) forces
: Nicam Un-mute, 1 = unmute
: CBI4 override, 1 => CBI[4] forced to 1 internally
: Controlthechoiceoftransmissionstandardstobesearchedforbytheautomaticstandardfunction
: 0F
: R/W
: 1010 0101
MONO OV
forces the audio signal to be muted.
can be used to forceto analoguesound. This may be useful in the case of marginal NICAM
reception to prevent automatic switching.
allows the NICAM decoder to be unmuted if the bit error rate is higher than the preset limit;
this overrides the automatic switching to FM or AM which would normally occur.
is used to override the 4th NICAM control bit (reserve sound switch) if required. This bit is
transmitted by the broadcaster to indicate that the analogue sound carrier is a backup of
the NICAM signal; this is usually the case. If the NICAM signal fails, the STV8203 will
automatically switch to backup sound if the received bit was set to 1. If this bit was set to
0 and bit 4 set to 0, the decoder will stay switched to analogue sound. If bit 4 is set to 1,
the received CBI4 is ignored. Note that if automatic standard is off, switching between
analogue and NICAM audio must be done manually.
(standardsearchactive whenbit= 1).The morechoices,thelongerthesearch time. Ifthesystem
in use can be identified by the characteristics of the video signal, for example by the chroma
demodulator,then only a single bit needs to be set. In this case, the AUTOSTANDARD function
willprogramthedemodulatorforthechosenstandard.If no bits areset,the AUTOSTANDARD
function is disabled andall registers need to be set manually.
bit 3 - Run check for standard 3 (L/L’ - AM/NICAM)
bit 2 - Run Check for Standard 2 (B/G - FM/NICAM)
bit 1 - Run check for standard 1 (B/G - Stereo)
bit 0 - Run check for standard 0 (I - FM/NICAM)
bit 6
bit 6
AUD-MX-CNT bits[6:4]
TIME 2 SETTING
010
UNMUTE
bit 5
bit 5
bit 7
C4 OV
X
bit 4
0
0
1
1
bit 4
bit 6
0
1
1
1
0
bit 3
bit 3
Muted (in case of B/G or I standard)
FM (in case of B/G or I standard)
MIN (in case of L/L’ standard)
STANDARD CHECK
bit 2
bit 2
TIME 1 SETTING
AO1 source
Muted
DAC
bit 1
bit 1
bit 0
bit 0