KR19990055569A - IC bus collision prevention device of digital satellite broadcasting set top box - Google Patents

Abstract

The present invention implements two types of audio decoders for implementing four channels of audio, and controls each device to enable and disable IIC bus lines to prevent data collisions between IIC buses. The present invention relates to an IIC bus collision avoidance device of a digital satellite broadcasting set top box. The present invention includes a channel decoder, an MPEG demultiplexer, a video encoder, first and second MPEG audio decoders for receiving and processing a signal transmitted through a satellite. In the digital satellite broadcasting set-top box, a device IIC bus control signal outputted through the GPIO port when the GPIO port is implemented in the microcomputer that controls the overall operation of the digital satellite broadcasting set-top box, and each device using the IIC bus is to be controlled. To control the addresses provided to each device. An address control unit and an IIC signal control unit which receives an address output from the address control unit as an enable and disable signal and selectively controls an IIC control signal output from an IIC controller in the MPEG demultiplexer, thereby preventing data collision between IIC buses. It will be prevented beforehand.

Description

IC bus collision avoidance device for digital satellite broadcasting set-top box

The present invention relates to IIC bus collision avoidance of a digital satellite broadcasting (DBS) set-top box (STB), in particular, to implement two types of audio decoders for controlling four channels of audio and controlling each device. The present invention relates to an IIC bus collision avoidance device of a digital satellite broadcasting set-top box which controls an IIC bus line by enabling and disabling to prevent a data collision between IIC buses.

In general, satellite broadcasting refers to a broadcasting method of retransmitting a broadcasting signal through a repeater in space for the purpose of receiving satellite broadcasting directly in a general home.

With recent technology, direct reception is possible due to the installation of a small antenna and a receiver, and thus it is widely used.

The advantage of satellite broadcasting is that it can provide high quality uniform broadcasting in a large area with less output than terrestrial broadcasting, and it is possible to prevent geographical reception disturbance and ghost phenomenon, local broadcasting is impossible, high reliability is required, and large investment There is a disadvantage that it is necessary.

In Korea, Mugunghwa satellite has been launched, and Mugunghwa satellite is composed of surrounding and auxiliary satellites, and it functions to relay signals emitted from the ground by stopping at 116 degrees east of 36000KM at low altitude.

Each satellite is equipped with twelve communication repeaters and three broadcast repeaters.

Telecom repeater is called FIXED SATELLITE (FS) and BANDWIDTH is 36M 14W. It is mainly used for TV broadcasting and long distance telephone relay.

The broadcast repeater is called BROADCASTING SATELLITE (BS), and its bandwidth is 27M and its output is 120W.

As above, satellite broadcasting is called DBS (DIRECT BROADCASTING SERVICE), and since 1995, it has been providing digital services.

At present, NHK of Japan and STAR TV satellite broadcasting of Hong Kong are already being received in Korea.

Digital DBS broadcasting has been successfully conducted by DIRECT_TV in the United States since 1994, and in Europe, the DVB standard has been prepared.

Digital DBS can broadcast four or more television signals simultaneously to one repeater using digital compressed signals, while analog DBS can only transmit one television signal per repeater.

Digital DBS is composed of three parts. Transmitter converts TV signal into digital TV signal and transmits it to satellite. Transmitter compresses video and audio data signal into digital signal according to Empok2 standard, and then configures it into PACKET STREAM. Create a digital television signal stream.

Multiple digital television signal streams are multiplexed in a transport multiplexer (TRANSPORT MULTIPLEXER) to form a transport stream (TRANSPORTS STREAM: TS) packet, which is then sent to the channel encoder. .

In the channel encoder, channel coding is performed to correct an error occurring during transmission, and the coded signal undergoes a modulation process to be transmitted to the satellite.

TS packets sent to the channel encoder are first converted into a random data stream during the ENERGY DISPERSION process.

Modulation uses QPSK because the power of the satellite repeater is limited, so power EFFICIENCY takes precedence over spectrum.

The modulated signal is converted to the KU-BAND (14GHZ) band in the upconverter and then amplified sufficiently in the HIGH POWER AMPLIFER (HPA) to be launched to the satellite through the transmit antenna.

The satellite repeater receives the signal of 14GHZ, amplifies it, converts it into 12GHZ, and retransmits it to the ground.

This signal is received by the home antenna, amplified by the LNB, converted to a signal of 1GHZ, and sent through the cable to the tuner.

The signal selected by the tuner is QPSK demodulated, de-multiplexed after transmission error correction in the FEC decoder, restored to MPEG2 TS PACKET, and decoded into video, audio, and data signals by the MPEG2 decoder.

The channel portion is composed of a channel coding portion and a modulation part.

Channel coding uses the FEC (FORWARD ERROR CORRECTION) method to correct errors in transmission. The FEC encodes and transmits data along with the redundancy to enable error detection and correction at the receiving end.

FEC adopts Reed Solomon code as the inter code, and uses CONCARCHATED coding with convolution interleaving in between.

The modulation part consists of a data randomizer, a pulse sharpening filter, a vena modem, and the like.

The channel coding and modulation schemes follow the current DVB specification, and the FEC uses Reed Solomon codes that can correct up to 8 vat errors.

Reed Solomon codes are relatively simple and have high error correction.

Since the size of the input packet is 188 bytes, we use the SHOORTENED RD CODE, RS, which is made from the RS code.

The MPEG 2 transport is randomly encoded by Reed Solomon after 187 bytes except the sync byte in the energy differential unit is converted into an error protection packet. Here RS coding also applies to sync bytes.

The receiver channel part is largely composed of an output part and an input part, and the output part is composed of an antenna, an LNB and a cable, and an input part is a tuner and a QPSK demodulator. It consists of an FEC decoder.

The output of the channel portion becomes an MPEG transport stream, which is restored by the MPEG decoder and restored by the TV and data signals.

The set-top box, a general satellite broadcasting receiver that performs this operation, implements two types of audio decoders to realize four-channel audio. When controlling each of these devices, an MPEG having an integrated IIC controller to avoid collisions between the IIC buses After initializing the demultiplexer, the clock and data lines of each device to be controlled by the IIC are simultaneously locked to each device so that each device has a different ID to prevent bus collisions.

However, this method also has the disadvantage that data collisions cannot be completely eliminated because clocks and data lines of various devices are simultaneously locked to each device.

Therefore, the present invention has been proposed to solve all the problems of the general digital satellite broadcasting receiver as described above.

The present invention implements two types of audio decoders for four-channel audio and controls each device to enable and disable IIC bus lines to prevent data collisions between IIC buses. The purpose is to provide an IIC bus collision avoidance device for digital satellite broadcasting set-top boxes.

Apparatus according to the present invention for achieving the above object,

Address control means for implementing a GPIO port in the microcomputer and controlling an address provided to each device when controlling each device using the IIC bus;

And an IIC signal control means for selectively controlling an IIC control signal output from an IIC controller in an MPEG demultiplexer by receiving an address output from the address control means as an enable and disable signal.

1 is a block diagram of an IIC bus collision avoidance device of a digital satellite broadcasting set-top box according to the present invention.

<Explanation of symbols for main parts of the drawings>

1: Microcom 6: Channel Decoder

8: MPEC Demultiplexer 10: MPEC Video Decoder

11: Video encoder 12: High frequency modulation section

13, 16: first and second MPEG audio decoder

17: Address control unit 18: IIC signal control unit

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

1 is a block diagram of an IIC bus collision avoidance apparatus for a digital satellite broadcasting set-top box according to the present invention.

Here, 1 is a micom that controls the entire operation of the set-top box according to the signal input from the front panel 2, and generates a control signal for controlling each device using the IIC bus through the GPIO port, 3 is the micom ( 1) is a central processing unit that controls the overall operation of the MPEG decoder through data communication, 4 is an Y-pyrom with information such as tuning frequency data, Viterbi code, symbol rate, etc., and 5 is the central processing unit (3 ) Is a DRAM that contains the data generated when the control operation is performed.

In addition, 6 is a channel decoder for tuning and demodulating the satellite signal through the antenna and the LNB to the original digital broadcast signal, 8 is an MPEG demultiplexer for separating the digital broadcast signal obtained by the channel decoder 6 into audio and video data. 10 is an MPEG video decoder for decoding video data obtained by the MPEG demultiplexer 8, 11 is a video encoder encoding a video signal decoded by the MPEG video decoder 10 into a video signal conforming to NTSC color format, 12 is a high frequency modulator that modulates a video signal obtained by the video encoder 11 into a high frequency signal in order to transmit it to another device.

13 is a first MPEG audio decoder which decodes MPEG audio data (PCM data) separated by the MPEG demultiplexer 8, and 14 is obtained by the video encoder 11 and the first MPEG audio decoder 13, respectively. Output terminal for transmitting video and audio signals to an output device.

15 is an audio logic circuit connected to the CPU 3 to process audio data obtained from the MPEG demultiplexer 8, and 16 is an MPEG audio data decoded through the audio logic circuit 16. The second MPEG audio decoder outputs a 2-channel audio signal.

The above configuration is an essential component of a general digital satellite set-top box, and the present invention provides an address provided to each device according to the IIC bus control signal output from the microcomputer 1 in the set-top box having the above-described configuration. Selectively controlling the IIC control signal output from the IIC controller in the MPEG demultiplexer 8 by receiving an address output from the address control unit 17 and an address output from the address control unit 17 as an enable and disable signal. And an IIC signal control unit 18.

The IIC signal controller 18 receives an address output from the address controller 17 as an enable and disable signal and buffers an IIC signal output from the MPEG demultiplexer 8 so as to buffer a channel decoder, a video encoder, And first to fourth tri-state buffers 18a to 18d for outputting the first and second MPEG audio decoder control signals.

Referring to the operation of the IIC bus collision prevention device of the digital satellite broadcasting set-top box according to the present invention configured as described above are as follows.

First, although not shown in the drawing, the switching mode power supply converts an external commercial AC power into a DC voltage, and then performs DC-DC conversion again to generate a plurality of DC voltages (including standby power and main power) to each stage of the system. Supply.

In this state, the channel decoder 6 receives the satellite signal through the antenna and the LNB in order to perform a demodulation process.

In this case, the antenna concentrates the weak signals transmitted to the surface and delivers the signal to the LNB. At this time, the signal focused on the antenna is selected and transmitted to the LNB through a feed hole.

The LNB is composed of a low noise amplifier and a block down converter, the signal received from the antenna is amplified and down-converted at the LNB, attenuated through the cable, passed to the tuner, and then amplified and converted to IF, Filtering process

Since the gain of the LNB is very large, about 50db, the noise characteristic of the entire receiver is determined by the noise FIGUTE and the influence of the tuner is small. Therefore, the LNB uses a low noise amplifier with a very good noise FIGUTE characteristic. The frequency of the input signal of the LNB is very high at 12 GHz. When the signal is sent to the tuner through the cable, the loss and noise effect due to the cable are severe.

Therefore, in the down converter, it is lowered to 1020-1340MHz (L-BAND), which is a relatively low frequency band, and transmitted through the cable.

This down converter uses a 10,678 GHz local oscillator, the LONG TERM FREQUENCY DRIFT of the local oscillator up to 2 MHz.

The power required for the LNB is DC 18V, and the current consumption is 18MA.

Meanwhile, the tuner module is a module in which the analog parts of the tuner unit and the QPSK demodulator are implemented in one shield case.

To tune the desired channel from the RF input signal, the tuner uses a PLL and a mixer to demodulate the analog in phase (I) and quadrature (Q) signals. These I and Q signals are sampled by the analog-to-digital converter and passed to the QPSK demodulator.

The automatic gain control input adjusts the IF signal level appropriately for analog QPSK demodulation and analog-to-digital conversion. It adjusts the gain so that the level of the I and Q signals is 2VPP at 1K ohm load.

This automatic gain control signal is received from the QPSK demodulator, with a control input voltage ranging from 1-5V and a dynamic range of 50db.

On the other hand, the baseband filter combines a demodulator and a digital filter to perform pulse sharpening, in which only amplitude components are filtered and the demodulator filters phase.

The PLL offsets the frequency value by the AFC value obtained by the demodulator after the IF is programmed to 479.5 MHz.

The LONG TERM FREQUENCY DRIFT is calibrated up to 2 MHz by the microcomputer 21, and the analog signal demodulated by I and Q in the tuner module is sampled at a 6-bit symbol rate in the analog / digital converter and input to the demodulator.

The demodulator digitally performs carrier tracking (CT), symbol timing recovery (STR), and automatic gain control (AGC) using the input digital I and Q signals.

Looking at the function of the demodulator more as follows.

First, the demodulator DEPUNCTURING the input symbol stream. That is, during encoding, a PUNCTURING symbol is replaced with a null symbol and converted into a symbol stream having a rate of 1/2.

On the other hand, the main functions of the Reed Solomon decoder are sync word detection, deinterleaving, Reed Solomon decoding, and derandomization. The input module converts a bitterdy decoded serial input bit stream into a byte stream and finds a sync word.

The de-interleaving rearranges the received byte stream. During the decoding of the decoded codeword, the decoding data is delayed by the codeword length due to the operation of the error detection of the MPEG packet and the addition of the data fail which is the error signal, so that the error correction is made simultaneously with the codeword output.

And de-randomization is pseudo de-randomization.

In the output module, when an error that cannot be corrected by the Reed Solomon decoder occurs, the transport packet error bit is set to "1" to inform the later MPEG demultiplexer 8.

The decoded byte, clock, data fail, data valid, and data streams are transferred to the MPEG demultiplexer 8 at the end to terminate the function of the channel decoder.

Here, the Reed Solomon decoder periodically detects the sync word in the input byte stream, initializes the pointer of the read / write of the de-interleave and periodically initializes the de-randomizer.

Meanwhile, the MPEG demultiplexer 8 separates video and audio data into respective data obtained by the channel decoder 6 as described above, and the first MPEG audio decoder 13 separates the MPEG audio data of the separated one channel. It is decoded and output to the audio output terminals 14b and 14c.

In addition, the separated video data is decoded by the MPEG video decoder 10 and then encoded by the video encoder 11 in a color format suitable for a broadcasting method, and output to the video output terminal 14a. To other devices.

In addition, the second MPEG audio decoder 16 decodes two-channel audio data among the audio data separated by the MPEG demultiplexer 8 and delivers it to the audio output terminal.

The audio and video output in this way is output to the monitor and speaker of the TV actually connected.

Herein, operations of an MPEG decoder including an MPEG video decoder and an MPEG audio decoder will be described in more detail.

MPEG decoders include transport, audio, and video decoding. The transport block performs multiplexing of any legitimate MPEG transport stream, and MPEG video decoder 10 codes MPEG2 MP / ML streams up to 15Mbps. The digital video data is output in CCIR601 format having NTSC resolution, and the video decoder 10 can display an image of 4; 3 (16: 9) aspect ratio on a TV having a 16: 9 (4: 3) aspect ratio. .

The MPEG audio decoder 13 and 16 can decode the MPEG layer 1/2 stream, and the decoded digital audio data is 16-bit PCM audio having an MPEG standard sampling frequency between 16 KHz and 48 KHz, and is embedded in the audio decoder. D / A converter converts the PCM data to analog audio signal.

On the other hand, video overlays and graphics are embedded in the MPEG video decoder 10.

The graphic information has 16 color information, and 4 pieces of TRANPATANCY are supported when the graphic information is combined with the video data.

On the other hand, in the general set-top box as described above, the IIC bus of the channel decoder 6, the video encoder 11, the first and second MPEG audio decoders 13 and 16, which are devices that use the IIC bus, are connected to the MPEG. It is controlled by an IIC controller embedded in the demultiplexer 8. In the present invention, the IIC control signal generated by the IIC controller is controlled without passing the signal directly to the corresponding device.

That is, a GPIO port is implemented in the microcomputer 1, and a control signal for controlling the IIC control signal is generated through the port.

Then, the address control unit 17 generates a switching signal for switching the IIC control signal by controlling an address for controlling the address of each device according to the IIC control control signal.

The first to fourth tri-state buffers 18a to 18d in the IIC signal controller 18 are disabled or enabled by the switching signal generated as described above to buffer the IIC signal generated by the MPEG demultiplexer 8. Passing or blocking the buffered output to each device prevents data collisions between the IIC buses.

As described above, in the present invention, when using two MPEG audio decoders for four-channel audio, each device using an IIC bus is enabled or disabled by enabling or disabling clock lines of each device. By having a different ID, it is possible to prevent data collisions between IIC buses in advance.

Claims (2)

In the digital satellite broadcasting set-top box including a channel decoder, an MPEG demultiplexer, a video encoder, and first and second MPEG audio decoders for receiving and processing a signal transmitted through a satellite, Implement a GPIO port in the microcomputer that controls the overall operation of the digital satellite set-top box, and control an address provided to each device according to a device control signal output through the GPIO port when controlling each device using an IIC bus. Address control means; And an IIC signal control means for selectively receiving an address output from the address control means as an enable and disable signal and selectively controlling an IIC control signal output from an IIC controller in the MPEG demultiplexer. IIC bus collision avoidance device for set top box. The method of claim 1, wherein the IIC signal control means receives the address output from the address control means as an enable and disable signal and buffers the IIC signal output from the MPEG demultiplexer so as to buffer the channel decoder, the video encoder, and the first. And first to fourth tri-state buffers for outputting the second MPEG audio decoder control signal.