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TDA9143/N1

I2C-bus controlled, alignment-free PAL/NTSC/SECAM decoder/sync processor

Philips Electronics 

Philips Semiconductors

I2C-bus controlled, alignment-free

PAL/NTSC/SECAM decoder/sync processor

Preliminary specification

TDA9143

FUNCTIONAL DESCRIPTION

The TDA9143 is an I2C-bus controlled, alignment-free

PAL/NTSC/SECAM colour decoder/sync processor which

has been designed for use with baseband chrominance

delay lines. For PALplus and EDTV-2 (60 Hz) signals

blanking facilities are included.

In the standard operating mode the I2C-bus address is 8A.

If the address input is connected to the positive supply rail

the address will change to 8E.

Input switch

The Y signal is internally connected to the switch. The

−(R−Y) and −(B−Y) output signals of the decoder first have

to be delayed in external baseband chrominance delay

lines. The outputs of the delay lines must be connected to

the UV input pins. If the RGB signals are not synchronous

with the selected decoder input signal, clamping of the

RGB input signals is possible by I2C-bus selection of ECL

(external RGB clamp mode) and by feeding an external

clamping signal to the CLP pin.

Also in external RGB clamp mode the VA output will be in

a high impedance OFF-state. The YUV outputs can be put

in 3-state mode by bus bit LPS (low power standby mode).

CAUTION

The voltage on the chrominance pin must never exceed

5.5 V. If it does, the IC enters a test mode.

The TDA9143 has a two pin input for CVBS or Y/C signals

which can be selected via the I2C-bus. The input selector

also has a position in which it automatically detects

whether a CVBS or Y/C signal is on the input. In this input

selector position, standard identification first takes place

on an added Y/CVBS and C input signal.

After that, both chrominance signal input amplitudes are

checked once and the input with the strongest

chrominance burst signal is selected. The input switch

status is read out by the I2C-bus via output bit YC. The

auto input detector indicates YC = 1 for a VBS input signal

(no chrominance component).

CVBS output

In the standard operating mode with I2C-bus address 8A,

a CVBS output signal is available on the address pin,

which represents either the CVBS input signal or the Y/C

input signal, added into a CVBS signal.

RGB colour matrix

CAUTION

The voltage on the Uin pin must never exceed 5.5 V.

If it does, the IC enters a test mode.

The TDA9143 has a colour matrix to convert RGB input

signals into YUV signals. A fast switch, controlled by the

signal on pin F and enabled by I2C-bus via EFS (enable

fast switch), can select between these YUV signals and

the YUV signals of the decoder. Mode FRGB = 1 (forced

RGB) overrules EFS and switches the matrixed RGB

inputs to the YUV outputs.

Standard identification

The standards which the TDA9143 can decode depend

upon the choice of external crystals. If a 4.4 MHz and a

3.6 MHz crystal are used then SECAM, PAL 4.4/3.6 and

NTSC 4.4/3.6 can be decoded. If two 3.6 MHz crystals are

used then only PAL 3.6 and NTSC 3.6 can be decoded.

Which 3.6 MHz standards can be decoded depends upon

the exact frequencies of the 3.6 MHz crystals. In an

application where not all standards are required only one

crystal is sufficient; in this instance the crystal must be

connected to the reference crystal input (pin 30). If a

4.4 MHz crystal is used it must always be connected to the

reference crystal input. Both crystals are used to provide a

reference for the filters and the horizontal PLL, however,

only the reference crystal is used to provide a reference for

the SECAM demodulator. To enable the calibrating circuits

to be adjusted exactly, two bits from I2C-bus subaddress

00 are used to indicate which crystals are connected to the

IC.

The standard identification circuit is a digital circuit without

external components. The search loop is illustrated

in Fig.3. The decoder (via the I2C-bus) can be forced to

decode either SECAM or PAL/NTSC (but not PAL or

NTSC). Crystal selection can also be forced. Information

concerning standard and which crystal is selected and

whether the colour killer is ON or OFF is provided by the

read out.

Using the forced-mode does not affect the search loop, it

does however prevent the decoder from reaching or

staying in an unwanted state. The identification circuit

skips impossible standards (e.g. SECAM when no

4.4 MHz crystal is fitted) and illegal standards (e.g. in

forced mode). To reduce the risk of wrong identification,

PAL has priority over SECAM. Only line identification is

used for SECAM. For a vertical frequency of 60 Hz,

SECAM can be blocked to prevent wrong identification by

means of bus bit SAF.

1996 Jan 17

6

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