tda9874h NXP Semiconductors, tda9874h Datasheet - Page 21

• Manufacturer Part Number: tda9874h
• Description: Digital Tv Sound Demodulator/decoder
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.3.4
Three bytes are required to define a 24-bit frequency
control word to represent the sound carrier (i.e. mixer)
frequency. These three bytes are stored at
subaddresses 3 to 5; subaddress 3 being the high byte.
Execution of the command starts only after all bytes have
been received. If an error occurs, e.g. a premature STOP
condition, partial data for this function are ignored. The
relation of the sound carrier frequency and the control
word is given in the following formula:
Table 18 Carrier 1 frequency register high byte (subaddress 3)
Table 19 Carrier 1 frequency register middle byte (subaddress 4)
Table 20 Carrier 1 frequency register low byte (subaddress 5)
7.3.5
The format is the same as for sound carrier 1, except
subaddresses 6 to 8 are used. Subaddress 6 holds the
high byte.
If the carrier 2 frequency register is used, it will be for either
the second FM sound carrier of a terrestrial or satellite
FM program or the NICAM sound carrier.
7.3.5.1
While NICAM mode is used, the sound carrier 2 frequency
should be set 2 kHz of the NICAM carrier frequency to
improve carrier loop settling. For a deviation of +2 kHz this
results in the following settings:
2000 Jun 26
data
Digital TV sound demodulator/decoder
B7
B7
B7
=
7
7
7
f
--------
C
f
C
mix
clk
ARRIER
ARRIER
Note
2
24
1
2
FREQUENCY REGISTER
FREQUENCY REGISTER
B6
B6
B6
6
6
6
B5
B5
B5
5
5
5
B4
B4
B4
4
4
4
21
where:
Example: A 5.5 MHz sound carrier frequency will be
generated by sending the following sequence of data
bytes to the TDA9874H (data is 7509333 in decimal
notation or 729555 in hexadecimal notation):
0111 0010 1001 0101 0101 0101.
The default setting at power-up is 0000 0000 for all three
bytes.
Standard B/G, D/K and L:
5.850 MHz + 2 kHz = 5.852 MHz = (79EAAAH).
Standard I:
6.552 MHz + 2 kHz = 6.554 MHz = (888AAAH).
data = 24-bit frequency control word
f
f
2
mix
clk
24
B3
B3
B3
3
3
3
= 12.288 MHz (clock frequency of mixer)
= 16777216 (number of steps in a 24-bit word size).
= desired sound carrier frequency
B2
B2
B2
2
2
2
B1
B1
B1
1
1
1
Product specification
TDA9874H
B0
B0
B0
0
0
0