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TDA9847

TV and VTR stereo/dual sound processor with digital identification

Philips Electronics 

Philips Semiconductors

TV and VTR stereo/dual sound processor

with digital identification

Preliminary specification

TDA9847

After that, when C4 is HIGH (see Table 2), the switch

positions of the SCART channel are changed in

accordance with the other control line levels.

When the supply voltage of the TDA9847 is not connected

(standby function), the control lines remain undisturbed.

The logic level combination 1000 of the control input ports

(C4, C3, C2 and C1) is not allowed (see Tables 1 and 2).

Operating mode selection

Tables 1 and 2 show the different operating modes of this

stereo decoder.

MUTE MODE

This IC has two different mute modes:

1. Mute mode.

2. Sound mute mode.

In the mute mode, when all control input lines are set LOW,

all AF channels are muted (‘fast mute’). Finally, the

integrators are reset provided the user does not leave this

mode (identification is disabled). When the user changes

this mode, the identification circuit starts with the

detection.

In the sound mute mode each AF channel can be

separately muted (0100 = main and 1100 = SCART). The

identification circuit is activated and the LEDs are on or off

in accordance with the detection status of this circuit.

MONO MODE

For the transmitter status mono the user must set the

TDA9847 in the mono mode with X001 or X010

(see Tables 1 and 2). The level combination X011 is

reserved for the AM sound (standard L), because in this

mode the de-emphasis is deactivated and the gain of the

AF signal from input to output is reduced from

6 dB to 0 dB. At the AF outputs the signal has the same

level for standards with FM or AM modulated sound

assuming the same modulation degree.

STEREO MODE

In this mode the choice between stereo and mono (‘forced

mono’) signals is common for both AF channel pairs. The

mode for main and SCART is achieved by control of the

main channel (see Tables 1 and 2).

DUAL MODE

In this mode there is no restriction to select AF inputs and

outputs independently in both channels.

EXTERNAL MODE

External sound sources, e.g. from SCART input, are fed to

both AF channel pair outputs. When the user chooses the

external mode of the main channel (see Table 1), the

identification circuit is still running, but the LEDs are

switched-off.

Programming of the main and SCART register

GENERAL INFORMATION

The switch positions of both AF channels are directly

controlled by the data of the main and SCART register.

These registers are programmable by a microcontroller.

In the 3-state mode the logic content of the C1, C2 and C3

control lines remains stored in the registers for main and

SCART, so the switch positions in the source selector do

not change. The logic content of these control lines can be

changed without changing the switch positions of the

source selector (preset position) to prepare the new

operating mode selection for the main or SCART channel.

The execution of this new mode is achieved by leaving the

preset position (3-state): When the C4 level goes LOW,

the logic content of the control lines C1, C2 and C3 are

valid for the main channel (see Table 1) and in the event

of HIGH the C1, C2 and C3 are valid for the SCART

channel (see Table 2).

The identification bits and the control lines influence the

operating mode selection for the AF switches in the source

selector and de-matrix, e.g. both AF channels are

programmed in the mono mode (X001,

see Tables 1 and 2). The LEDs are switched-off. When

the identification circuit detects the stereo identification

frequency (fs = 117 Hz) the de-matrix is immediately

switched in the stereo mode without changing the control

line levels. The stereo signals are routed to all AF outputs.

In the event of dual frequency detection (fD = 274 Hz) both

dual sounds are fed to the AF output pairs.

MICROCONTROLLER WITH 3-STATE OUTPUT PORTS

Figure 10 shows an example of an application circuit for

TDA9847 (VP = 4.5 to 8.8 V) in conjunction with a

microcontroller, which has a LOW/high-ohmic/HIGH

output port to control the main and SCART channel (C4

control line). For the C1, C2 and C3 line the microcontroller

requires only LOW/HIGH output ports. Two resistors RC4A

and RC4B are necessary for the C4 line to generate the

3-state voltage. The values and tolerances of these

components are given in Fig.10.

1995 May 23

7

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