MSP3401G datasheet(96/104 Pages) MICRONAS

96 / 104 page

MSP 34x1G

PRELIMINARY DATA SHEET

Micronas

6.4.4. NICAM Error Rate Register

Average error rate of the NICAM reception in a time

interval of 182 ms, which should be close to 0. The ini-

tial and maximum value of ERROR_RATE is 2047.

This value is also active if the NICAM bit of

MODE_REG is not set. Since the value is achieved by

filtering, a certain transition time (approx. 0.5 sec) is

unavoidable. Acceptable audio may have error rates

up to a value of 700 int. Individual evaluation of this

value by the controller and an appropriate threshold

may define the fallback mode from NICAM to FM/

AM-Mono in case of poor NICAM reception.

The bit error rate per second (BER) can be calculated

by means of the following formula:

BER = ERROR_RATE * 12.3*10−6 /s

6.4.5. PLL_CAPS Readback Register

It is possible to read out the actual setting of the

PLL_CAPS. In standard applications, this register is

not of interest for the customer.

6.4.6. AGC_GAIN Readback Register

It is possible to read out the actual setting of

AGC_GAIN in Automatic Gain Mode. In standard

applications, this register is not of interest for the cus-

tomer.

6.4.7. Automatic Search Function for FM-Carrier

Detection in Satellite Mode

The AM demodulation ability of the MSP 34x1G offers

the possibility to calculate the “field strength” of the

momentarily selected FM carrier, which can be read

out by the controller. In SAT receivers, this feature can

be used to make automatic FM carrier search possi-

ble.

For this, the MSP has to be switched to AM-mode

(MODE_REG[8]),

FM-Prescale

must

set

7Fhex = +127dec, and the FM DC notch (see section

6.5.7.) must be switched off. The sound-IF frequency

range must now be “scanned” in the MSP-channel 2 by

means of the programmable quadrature mixer with an

appropriate incremental frequency (i.e. 10 kHz). After

each incrementation, a field strength value is available

at the quasi-peak detector output (quasi-peak detector

source must be set to FM), which must be examined

for relative maxima by the controller. This results in

either continuing search or switching the MSP back to

FM demodulation mode.

During the search process, the FIR2 must be loaded

with

the

coefficient

set

“AUTOSEARCH”,

which

enables small bandwidth, resulting in appropriate field

strength characteristics. The absolute field strength

value (can be read out of “quasi-peak detector output

FM1”) also gives information on whether a main FM

carrier or a subcarrier was detected; and as a practical

consequence, the FM bandwidth (FIR1/2) and the

deemphasis (50

µs or adaptive) can be switched

accordingly.

Due to the fact that a constant demodulation frequency

offset of a few kHz leads to a DC level in the demodu-

lated signal, further fine tuning of the found carrier can

be achieved by evaluating the “DC Level Readout

FM1”. Therefore, the FM DC Notch must be switched

on, and the demodulator part must be switched back to

FM-demodulation mode.

For a detailed description of the automatic search

function, please refer to the corresponding MSP Win-

dows software.

ERROR_RATE

00 57hex

Error free

0000hex

maximum error rate

07FFhex

PLL_CAPS

02 1Fhex L

minimum frequency

1111 1111

FFhex

nominal frequency

0101 0110

56hex

RESET

maximum frequency

0000 0000

00hex

PLL_CAPS

02 1Fhex H

PLL open

xxxx xxx0

PLL closed

xxxx xxx1

AGC_GAIN

02 1Ehex

max. amplification

(20 dB)

0001 0100

14hex

min. amplification

(3 dB)

0000 0000

00hex

MSP3401G Datasheet(PDF) 96 Page - Micronas

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