
1998 Apr 27
30
Philips Semiconductors
Preliminary specification
Digital TV sound demodulator/decoder
TDA9874H
7.3.13
NICAM L
OWER
E
RROR
L
IMIT
R
EGISTER
(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 U
PPER
E
RROR
L
IMIT
R
EGISTER
(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
A
UDIO
M
UTE
C
ONTROL
R
EGISTER
(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)
7
6
5
4
3
2
1
0
B7
B6
B5
B4
B3
B2
B1
B0
7
6
5
4
3
2
1
0
B7
B6
B5
B4
B3
B2
B1
B0
7
6
5
4
3
2
1
0
MUTI
2
S
MUTOUT
7.3.16
DAC O
UTPUT
S
ELECT
R
EGISTER
(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
7
6
5
4
3
2
1
0
DGS1
DGS0
DOS1 DOS0
DGS1 DGS0
DAC GAIN
(dB)
0
0
1
1
0
1
0
1
0
3
6
9
DOS1 DOS0
SIGNAL SOURCE
LEFT
RIGHT
0
0
1
1
0
1
0
1
FM/AM
NICAM left
FM/AM
FM/AM
FM/AM
NICAM right
NICAM M1
NICAM M2