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TDA9144 датащи(PDF) 9 Page - NXP Semiconductors |
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TDA9144 датащи(HTML) 9 Page - NXP Semiconductors |
9 / 44 page 1996 Jan 17 9 Philips Semiconductors Preliminary specification I2C-bus controlled, alignment-free PAL/NTSC/SECAM decoder/sync processor with PALplus helper demodulator 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 For EDTV-2 (system M, 60 Hz, 525 lines) outside the letter box area, blanking is possible and takes place on lines HOB HBC SNR HELPER BLANKING 0 X X OFF 10 X ON 110 OFF 111 ON 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. |
Аналогичный номер детали - TDA9144 |
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Аналогичное описание - TDA9144 |
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