TDA9144 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TDA9144

I2C-bus controlled, alignment-free PAL/NTSC/SECAM decoder/sync processor with PALplus helper demodulator

Philips Electronics 

Philips Semiconductors

I2C-bus controlled, alignment-free PAL/NTSC/SECAM

decoder/sync processor with PALplus helper demodulator

Preliminary specification

TDA9144

In case of a PALplus input signal, the standard

identification system of the TDA9144 only determines PAL

and needs additional I2C-bus information for PALplus, via

bus bits MACP, HD, HOB and HBC.

Bus bit MACP determines whether the 4.43 chrominance

signal component of the CVBS input signal should be

suppressed by a 4.43 trap or not. For MACP = 1 the

chrominance suppression takes place outside the

TDA9144.

The HD bit (helper demodulation) enables PALplus helper

demodulation on the U phase (i.e. the B−Y demodulation

axis). As there is only a 4.43 notch for the demodulated

helper, an external notch filter is necessary to suppress the

8.86 MHz demodulation product and resolve the

baseband helper signal. The demodulated helper

luminance signal is always led to a notch filter (4.43 MHz,

no bypass here), then multiplexed with the regular 430

letter box lines luminance signal and led to the output Yout.

The black level of the luminance signal is internally

clamped with a large time constant to the black level

generated by the helper demodulator.

Also bus bits HD and MACP determine the presence of a

black set-up voltage (with luminance scaling of a factor

0.8) and a helper set-up voltage for the demodulated

helper signal on the output signal Yout. These set-up

voltages are necessary for PALplus signal post processing

outside the TDA9144. The set-up voltages are also

multiplexed into a reference line 22, combined with the

demodulated helper reference of line 23 and luminance

reference of line 623, both present in every PALplus signal

for correct PALplus reference post processing (see Fig.5).

Additional helper blanking bits (HOB, HBC) determine

whether the helper signal has to be blanked or blanked

conditionally depending on the signal-to-noise ratio bit

SNR. Helper blanking can only take place on a norm sync

signal, indicated by output bit NRM = 1. Table 1 is valid in

50 Hz or 60 Hz mode.

Table 1 Helper blanking modes

HOB

0

1

1

1

HBC

X

0

1

1

SNR

X

X

0

1

HELPER

BLANKING

OFF

ON

OFF

ON

For EDTV-2 (system M, 60 Hz, 525 lines) outside the letter

box area, blanking is possible and takes place on lines

230 to 312 and 493 to 49(1) when helper blanking is

activated.

The TDA9144 can handle PALplus signals in either CVBS

or Y/C format. In case of a Y/C signal, the modulated

helper must be available on the chrominance input pin (C).

The use of the 4.43 trap will not be necessary, as the

chrominance and luminance components of a Y/C signal

are already separated, so the 4.43 trap for the letter box

luminance is bypassed (not for the demodulated helper

signal). During helper demodulation, the internal chroma

bandpass filter is bypassed.

For PALplus the I2C-bus Hue bits HU0 to HU5 are used to

adjust for a correct helper demodulator phase. This has no

effect on the R−Y and B−Y demodulator phase for PAL.

Table 2 gives an overview of the possible PALplus modes

and their effects in the TDA9144. The table is only valid for

a 50 Hz system. In 60 Hz system mode the columns for

line 22, 23b and 623a do not exist, and using the MACP

and HD bits has no effect on the 60 Hz signal.

• Mode 1 → normal PAL

• Mode 2 → PAL with MACP processing

• Mode 3 → full PALplus

• Mode 4 → PALplus without MACP processing (helper

only)

• Mode 5 → near_norm or no_norm sync condition

• Mode 6 → norm sync condition with fast blanking active

• Mode 7 → system ident not identified as PAL.

The indications a and b for the lines 22, 23 and 623

respectively stand for the first half and the second half of a

line.

The signalling bits in line 23 (see Fig.5) are processed in

the same manner as letter box luminance lines in the

TDA9144. Signalling bit decoding and PALplus

identification is done externally with I2C-bus as

communication link to the TDA9144 for bus bits MACP,

HD, HOB, and HBC.

(1) For system M the line numbers start with the first equalizing

pulse in field 1, but the internal line counter starts counting at

the first vertical sync pulse in field 1. This line number

notation is used here and in Fig.9.

1996 Jan 17

9

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