
2000 Aug 04
16
Philips Semiconductors
Product specication
Digital TV sound demodulator/decoder
TDA9874A
7I2C-BUS CONTROL
7.1
Introduction
The TDA9874A is controlled only via the I2C-bus. Control
is exercised by writing data to one or more internal
registers. Status information can be read from an array of
registers to let the controlling microprocessor determine
whether any action is required.
The device has an I2C-bus slave transceiver in
accordance with the fast-mode specification with a
maximum speed of 400 kbits/s. Information about the
I2C-bus can be found in brochure
“I2C-bus and how to use
it” (order number 9398 393 40011). To avoid conflicts in a
real application with other ICs providing similar or
complementing functions, there are four possible slave
addresses available, which can be selected by
pins ADDR1 and ADDR2 (see Table 6).
Table 6
Possible slave addresses
The I2C-bus interface remains operational in the standby
mode of the TDA9874A to allow the device to be
reactivated via the I2C-bus.
The device will not respond to a ‘general call’ on the
I2C-bus, i.e. when a slave address of 0000 000 is sent by
a master.
7.2
Power-up state
After Power-on reset respectively at power-up the device
is in the following state:
All outputs muted
No sound carrier frequency loaded
General purpose I/O pins ready for input (HIGH)
Input SIF1 selected with:
– AGC on
– SIF 10 dB attenuator off
– Small hysteresis.
Demodulators for both sound carriers set to FM with:
– Identification for B/G, D/K, identification mode ‘slow’
– Level adjustment set to 0 dB
– De-emphasis 50
s
– Dematrix set to mono
– Adaptive de-emphasis off.
Analog outputs are muted and connected to DACs
Digital audio interface all outputs off
Monitor set to carrier 1 DC output.
After Power-on reset or power-up, a device initialization
has to be performed via the I2C-bus to put the TDA9874A
into the proper mode of operation, in accordance with the
desired TV standard, etc. This can be done by writing to all
registers with a single I2C-bus transmission (such as a
refresh operation) or by writing selectively only to those
registers, the contents of which need to be changed with
regard to the power-up state. Easy Standard Programming
(ESP) can also be used.
ADDR2
ADDR1
SLAVE ADDRESS
A6
A5
A4
A3
A2
A1
A0
0
1011000
0
1
1011001
1
0
1011010
1
1011011