TDA9874H datasheet(30/56 Pages) PHILIPS

30 / 56 page

1998 Apr 27

Philips Semiconductors

Preliminary speciﬁcation

Digital TV sound demodulator/decoder

TDA9874H

7.3.13

NICAM LOWER ERROR LIMIT REGISTER (NLELR)

When the auto-mute function is enabled

(see Section 7.3.11) and the NICAM bit error count is

lower than the value contained in this register, the NICAM

signal is selected (again) for reproduction. See also

Section 7.3.14.

The default setting at power-up is 00010100.

Table 37 NICAM Lower Error Limit Register

(subaddress 16)

7.3.14

NICAM UPPER ERROR LIMIT REGISTER (NUELR)

When the auto-mute function is enabled

(see Section 7.3.11) and the NICAM bit error count is

higher than the value contained in this register, the signal

of the first sound carrier (i.e. FM mono or AM sound) or the

analog mono input is selected for reproduction.

The difference between upper and lower error limit

constitutes a hysteresis to avoid frequent switching

between NICAM and the program on the first sound

carrier.

The default setting at power-up is 01010000.

Table 38 NICAM Upper Error Limit Register

(subaddress 17)

7.3.15

AUDIO MUTE CONTROL REGISTER (AMCONR)

Only bits 6 and 2 are used. The state of the unused bits

should be set to logic 1. When any of these bits is set

HIGH, the corresponding pair of output channels will be

muted. A LOW bit allows normal signal output.

The default setting at power-up is 11111111.

Table 39 Audio Mute Control Register (subaddress 18)

76543210

543210

765

−

MUTI2S

−−−

MUTOUT

−−

7.3.16

DAC OUTPUT SELECT REGISTER (DACOSR)

This register is used to define the signal source to be

entered into the DAC. The DAC is used for signal output

from digital sources at analog outputs.

The two combinations of FM and NICAM shown in

Table 42 apply to the (rare) condition that three different

languages are being broadcast in an FM + NICAM system.

They allow for a two-out-of-three selection for special

applications. Note that the controlling microprocessor has

to assure that the FM dematrix is set to the mono position.

Some extra gain can be introduced at the input to the DAC

to provide a coarse level adjust function.

The default setting at power-up is 00000000.

Bits B2, B4, B5 and B6 are not used and should be set to

logic 0.

Table 40 DAC Output Select Register (subaddress 19)

Table 41 Selection of DAC gain

Table 42 Signal source left and right

654

DGS1

−−−

DGS0

−

DOS1 DOS0

DGS1 DGS0

DAC GAIN

(dB)

DOS1 DOS0

SIGNAL SOURCE

LEFT

RIGHT

FM/AM

NICAM left

NICAM right

FM/AM

NICAM M1

FM/AM

NICAM M2

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