Hitachi CL2554AN, Service Manual

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Service manual CL2554AN / CL2854AN
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This mode can be used for input only operation of the port.
Special port for LED
Pin 10 and 11 have the same functionality as the general I/O pins but in addition, their current source
and sink capacity is 8 mA instead of 4 mA. These pins are used for driving LED’s via a series current
limiting resistor.
m -Controller I/O pin configuration and function table
pin name configuration description
Stand by TV ON
1 n.u. High impedance High impedance not used
2 SCL Open Drain Open Drain Serial clock line
3 SDA Open Drain Open Drain Serial data line
4 SECAM L’ High impedance Push Pull SIF filter switching
5 OCP High impedance High impedance Over Current Protection
( Switch the set OFF if
the voltage on this pin is
<2.7V )
6 - High impedance High impedance For factory use only
7 Key in High impedance High impedance Local keyboard input
8 S/SW High impedance See table above external video switch
10 Red LED High impedance Open Drain
11 Green LED Open Drain High impedance
62 Audio mute Push Pull Push Pull High in stand by mode
5-5 Sound processing
Analogue sound IF - input section
The input pins and ANA_IN- offer the possibility to connect sound IF sources to the MSP
3415D. The analogue-to-digital conversion of the pre-selected sound IF signal is done by an A/D
converter, whose output is used to control an analogue automatic gain circuit (AGC), providing an
optimal level for a wide range of input levels.
Quadrature Mixers
The digital input coming from the integrated A/D converter may contain audio information at a
frequency range of theoretically 0 to 9 MHz corresponding to the selected standards. By means of two
programmable quadrature mixers, two different audio sources ; for example, NICAM and FM-mono,
may be shifted into baseband position.
Phase and AM discrimination
The filtered sound IF signals are demodulated by means of the phase and amplitude discriminator block.
On the output, the phase and amplitude is available for further processing. AM signals are derived from
the amplitude information, whereas the phase information serves for FM and NICAM demodulation.
NICAM decoder
In case of NICAM - mode, the phase samples are decoded according the DQPSK - coding scheme. The
output of this block contains the original NICAM bitstream.