| This paper introduces the design method of large scale video matrix switching system based the Coaxitron Technique, and summarizes the application of AD8111 and MB90092 in Video Matrix Switcher. It introduces the general design solution and the specific hardware and software design of the system in detail. It describes the features of MB90092 and its application in video Chinese character superimposing. The chip AD8111 and its operating principle are introduced in this paper. The hardware circuit and the software method of character superimposing with the use of AT89S51 is given. Some problems which should be paid attention to in software and hardware design are also described.This system researches into the modular design scheme with great capabilities of switch matrices in order to expand capabilities of switch matrices, improve their performance and induce the cost. The first part of this thesis, the design of large scale video switch matrix is discussed in detail. The second part is the research on the coaxitron technique. In the part of video switch matrix, the hardware and software design of the system is introduced in detail. In hardware design, the system is divided into four parts according to the function: main board, switch board, caption board and coaxitron board, and by this means, decrease the design difficulty and facilitate adjusting the video switch matrix's scale and function. In the part of coaxitron board design, according to the basic principle of VBI (Vertical Blanking Interval), this paper acquires related experience from the advanced technique for delivering of control signals during the period of VBI. It introduces a scheme using a single coaxial-cable to transmit video signals and control signals simultaneously, in which the key technique is the transmission of control signals in the vertical blanking interval of video signals.Finally the main issues that need to be considered in hardware and software debugging are pointed out. |
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