MAX9217 video link in the transmission of audio-MAX9217 data, video links, audio data – Communications Industry
Parallel data series data sent to the receiver (MAX9218), the receiver then the serial data into parallel data.
The circuit design was used for a couple of torque at low cost braided cable (such as Ethernet, commonly used in UTP-CAT5 cable) and control signals from the video graphics controller (Processor) or LCD transmission Plasma Flat Panel Monitor. Transmission distance of more than Lom. The binding of simple circuit group, use the transmission line for low-cost cable, automotive, Miriam table, medical equipment, the ideal solution for displaying video. The circuit group not only can transmit video signals between two points, and sometimes People also want the ability to send audio signals. This article will discuss how to use the deleted video signal control signal through channel audio data to the screen.
1 link features and video data formats
MAX9217 serializer with 27-bit parallel input bus fares up to 35Mb / s. In 27 of the 18 is the video: RGB data: three color of all the employed in June, and the remaining 9 are the control signals. 9 control signals in the first three mentioned and vertical and horizontal synchronization data RGB: VSYNC (C0), HSYNC (c1) and ENAB (C2). The remaining six control bits (C3 to C8) control signals for the other. In this case, we use six bits of control on the transmission of audio data. MAX9217 can be 18 years or data of 9-bit RGB is converted to data series data, control, and then transmitted via LVDS link their. Blanking period in video display control data sent. RGB data signal Empowerment (ENAB) instructions.
MAX9218 data that is received, it will become the same with the MAX9217 parallel format input data. Similarly, when the MAX9218 output data in parallel, according to the serial LVDS link the time to rebuild the bus clock. l The figure shows the MAX9217 and MAX9218 between video and configuration control and data link connection in the process.
2 digital audio data types and transmission formats
Digital audio data a number of different formats. 3 The most commonly used digital audio format is the sample (PCM), MPEG Audio Layer 3 (MP3) and digital ATSC standards compression audio (AC3). PCM digital audio is a CD-ROM or DVD data used. To the left and right signal channel audio sampled PCM digital signal, frequency sampling of 44. lkHz, precision 16-bit or 32-bit. Therefore, the accuracy is 16 bits, the rate of PCM audio data 1.41Mb / s, 32 bits of 2.42Mb / s. 1 700MBCD save About 60 minutes of data format of 16-bit PCM music.
MP3 is an MP3 player, audio format used for compressing PCM audio data. rate Data stereo MP3 112kb / s to 128kb / s. For this type of data, the decoded MP3 digital audio sound quality with the same CD. AC3 digital TV, HDTV and Digital Cinema Audio encoding standard. Stereo AC3 encoded data rate is 192kb / s.
To restore the audio signal can be encoded audio data in audio decoder The PCM decoder generates digital data, sent to the audio DAC with time signals back to analog audio. On the contrary, there is no data encryption digital audio directly into the audio DAC. Encoding or decoding audio data commonly used serial digital audio interface is the Inter? Audio IC bus (12S). Figure 2 shows the 12S interface configuration and timing diagram. The limit of each word in the audio signal was Logo. It is used in our configuration mode l. application The rising edge of SCK signal, the data has been attached to the receiver, but when SCK is low when no data is received.
Use the MAX9217 and MAX9218 serial link between the simulation interface 12S, the audio data can be transmitted from the graphics controller at the remote end. We will control bits C3 and C4 were assigned to the SD card and WAS signal. The SCK clock, if you want to send the PCM digital audio, you can directly use the MAX9218 to restore the pixel clock PCLK-0UT. For the transfer of MP3 audio or AC3, can be used as SCK clock control bit generation C5 roughly half the pixel clock speed. Figure 3 shows the situation of these two time waveforms. To prevent overflow of receiver, most of the interfaces ix3 need throttle control and continuously send data, you can set SCK low, the direct implementation of throttle control. Figure 3 in case 1, the work can not be set low for the SCK signal, you can use the chip select pin closed SG receptor. In this case, the CS signal assigned to C6.
3 delivery system needs to board Play audio signal to be sent to the audio data DAC PCM data or decode MP3 and AC3, and then sent to the audio DAC. In the absence of the inverse of the channel is sent to the controller handshake signals back to the master clock decoder must be synchronized with the pixel clock to prevent data overflow or underflow. Figure 4 shows the data coding and audio coding reproductive system structure.
Map with three interfaces 12S. From left, the first and second identical 12S interface data rate can reach 35MHz. The third interface? Headphone Amplifiers MAX9850DirectDfive interface, fixed interest rate of multiple audio sample Rate. MAX9491 multiple clock clock SCK2 Generator, decoder, FIFO, and the MAX9850 synchronous clock. Package MAX9491 offers two points of the Office of PLL, is ideal for this application, the synthesizer frequency. Case 1 is applied to decode the PCM audio data to provide the graphics controller, part of two panel cases for decoding compressed data. For case 1 the throttle control to achieve the CS pin, two types of circumstances to achieve through the SCK clock inactive. The comparison of these two implementations, we If data does not require an audio PCM time largely blind (Table 1) does not use the audio decoder circuitry, cost less than Case 2. Therefore, if the driver graphics, etc. to MP3 or AC3 encoded audio data to generate PCM data stream, the proposed transmission of data directly on the link. [Keywords]: MAX9217 Video Data Link Audio Commentary In Small Large About the Author
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