DATA SHEET
MSP 34x0G
6.3. Manual/Compatibility Mode:
6.3.1.1. Function in Automatic Sound Select Mode
Description of Demodulator Write Registers
The Automatic Sound Select feature (MODUS[0]=1)
includes the procedure mentioned above. By default, the
internal ERROR_RATE threshold is set to 700dec. i.e.:
6.3.1. Automatic Switching between NICAM and
Analog Sound
– NICAM → analog Sound if ERROR_RATE > 700
– analog Sound → NICAM if ERROR_RATE < 700/2
In case of bad NICAM reception or loss of the
NICAM-carrier, the MSP 34x0G offers an Automatic
Switching (fall back) to the analog sound (FM/AM-
mono), without the necessity for the controller of reading
and evaluating any parameters. If a proper NICAM sig-
nal returns, switching back to this source is performed
automatically as well. The feature evaluates the NICAM
ERROR_RATE and switches, if necessary, all output
channels which are assigned to the NICAM-source, to
the analog source, and vice versa.
The ERROR_RATE value of 700 corresponds to a
BER of approximately 5.46*10-3 /s.
Individual configuration of the threshold can be done
using Table 6–5. However, the internal setting used by
the standard selection is recommended.
The optimum NICAM sound can be assigned to the
MSP output channels by selecting one of the “Stereo
or A/B”, “Stereo or A”, or “Stereo or B” source chan-
nels
An appropriate hysteresis algorithm avoids oscillating
effects (see Fig. 6–1). STATUS[9] and C_AD_BITS[11]
(Address: 0023hex) provide information about the actual
NICAM-FM/AM-status.
6.3.1.2. Function in Manual Mode
Selected Sound
NICAM
If the manual mode (MODUS[0]=0) is required, the
activation and configuration of the Automatic Switching
feature has to be done as described in Table 6–6. Note
that the channel matrix of the corresponding out-
put-channels must be set according to the
NICAM-mode and need not to be changed in the FM/
AM-fallback case.
analog
sound
ERROR_RATE
threshold/2
threshold
Example:
Fig. 6–1: Hysteresis for Automatic Switching
Required threshold = 500: bits[10:1] = 00 1111 1010
Table 6–5: Coding of Automatic NICAM/Analog Sound Switching;
Automatic Sound Select is on (MODUS[0] = 1)
Mode
Description
AUTO_FM [11:0]
ERROR_RATE- Source Select:
Threshold/dec
Addr. = 00 21
Input at NICAM Path1)
hex
1
Automatic Switching with
internal threshold
bit[11:0] = 0
700
NICAM or FM/AM,
depending on
Default
ERROR_RATE
2
Automatic Switching with
external threshold
(Customizing of Automatic
Sound Select)
bit[11]
bit[10:1] = 25...1000
= threshold/2
= 0
set by customer;
recommended
range: 50...2000
bit[0]
= 1
3
Forced Analog Mono
bit[11]
bit[10:1] = ignored
bit[0] = 1
= 1
always FM/AM
1)
The NICAM path may be assigned to “Stereo or A/B”, “Stereo or A”, or “Stereo or B” source channels
(see Table 2–2 on page 12).
Micronas
May 27, 2003; 6251-476-1DS
89
MICRONAS [ MICRONAS ]
