MSP3410D datasheet(24/83 Pages) MICRONAS

24 / 83 page

MSP 34x0D

PRELIMINARY DATA SHEET

Micronas

6.4.2. AUTO_FM/AM: Automatic Switching

between NICAM and FM/AM-Mono

In case of bad NICAM transmission or loss of the

NICAM carrier, the MSPD offers a comfortable mode to

switch back to the FM/AM-Mono signal. If automatic

switching is active, the MSP internally evaluates the

ERROR_RATE. All output channels which are assigned

to the NICAM source are switched back to the

FM/AM-Mono source without any further CCU instruc-

tion, if the NICAM carrier fails or the ERROR_RATE

exceeds the definable threshold.

Note, that the channel matrix of the corresponding out-

put channels must be set according to the NICAM

mode and need not be changed in the FM/AM fall-back

case. An appropriate hysteresis algorithm avoids oscil-

lating effects. The MSB of the Register C_AD_BITS

(Addr: 0023hex) informs about the actual NICAM

FM/AM Status (see section 6.6.2. on page 32).

There are two possibilities to define the threshold

deciding for NICAM or FM/AM-Mono (see Table 6–4):

1. default value of the MSPD (internal threshold = 700,

i.e. switch to FM/AM if ERROR_RATE > 700)

2. definable by the customer (recommendable range:

threshold = 50...2000, i.e. Bits [10...1] = 25...1000).

Note: The auto_FM feature is only active if the NICAM

bit of MODE_REG is set.

Table 6–4: Coding of automatic NICAM FM/AM switching (reset status: mode 0)

Mode

Auto_FM [11...0]

Addr. = 0021hex

Selected Sound at the

NICAM Channel Select

Threshold

Comment

default

Bit

[0]

= 0

Bits [11...1] = 0

always NICAM

none

Compatible to MSP 3410B,

i.e. automatic switching is

disabled

Bit

[0]

= 1

Bit

[11...1] = 0

NICAM or FM/AM,

depending on

ERROR_RATE

700 dec

automatic switching with

internal threshold

Bit

[0]

= 1

Bit

[10...1] = 25..1000 int

= threshold/2

Bit

[11]

= 0

NICAM or FM/AM,

depending on

ERROR_RATE

set by

customer

automatic switching with

external threshold

Bit

[11]

= [0] = 1

Bit

[10...1] = 0

always FM/AM

none

Forced FM-Mono mode, i.e.

automatic switching is

disabled

MSP3410D Datasheet(PDF) 24 Page - Micronas

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