TDA9874A Philips Semiconductors, TDA9874A Datasheet - Page 43

• Manufacturer Part Number: TDA9874A
• Description: Digital TV sound demodulator/decoder
• Manufacturer: Philips Semiconductors

Philips Semiconductors
10.3.17 S
This register is used to define the signal source to be
entered into the DAC. The stereo DAC output can be
routed to the analog stereo output pins, depending on the
setting in the AOSR; see Section 10.3.18.
A simplified setting is possible, if automatic FM dematrix
switching (see Section 10.3.9) and auto-select
(see Section 10.3.18) is applied.
The two combinations of FM and NICAM shown in
Table 50 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. It should be noted that the controlling
microprocessor has to assure that the FM dematrix is set
to the mono position or that IDSWFM is set HIGH.
An additional Automatic Volume Level (AVL) control
function is implemented, which provides a constant output
level of 23 dB (FS) for input levels between 0 and
to choose from, i.e. 2, 4 or 8 s.
The automatic stereo DAC switching, operating similar to
the mono DAC switching, is shown in Table 56.
The default setting after power-on reset is ‘0000 0000’.
Bits 2 and 6 are not used and should be set to logic 0.
Table 47 Stereo DAC output select register
Table 48 Selection of stereo DAC gain
1999 Dec 03
SDGS1 0 AVL
29 dB (FS). There are some fixed decay time constants
Digital TV sound demodulator/decoder
7
SDGS1
(SDACOSR)
0
0
1
1
(subaddress 19)
6
TEREO
5
1
DAC O
AVL
4
0
UTPUT
SDGS0
SDGS0 0 SDOS1 SDOS0
0
1
0
1
3
S
ELECT
2
R
EGISTER
DAC GAIN
1
(dB)
0
3
6
9
0
43
Table 49 AVL control mode
The AVL attack time is always 10 ms.
Table 50 Signal source left and right
The auto-select function is available only if SDOS1 and
SDOS0 are set to ‘00’ or ‘01’. Matrixing can be set in the
analog output select register.
10.3.18 A
This register is used to define both the signal source to be
output at the analog outputs and the output channel
selector mode.
The DAC outputs are automatically muted in the event that
one of the analog inputs is selected for output.
The
outputs, it is not available for analog input signals.
The default setting after power-on reset is ‘0000 0000’.
SDOS1
AVL1
0
0
1
1
0
0
1
1
L
------------- -
+
2
R
NALOG
position of the matrix applies only to the DAC
SDOS0
AVL0
0
1
0
1
0
1
0
1
O
UTPUT
off or reset
short decay (2 s)
medium decay (4 s)
long decay (8 s)
SIGNAL SOURCE STEREO
NICAM left
S
FM/AM
FM/AM
FM/AM
ELECT
LEFT
Preliminary specification
R
AVL MODE
EGISTER
DAC
TDA9874A
NICAM right
NICAM M1
NICAM M2
(AOSR)
FM/AM
RIGHT