TV video output for the EB675001DIP

  
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This application note describes creating a dumb framebuffer with PAL composite TV output for the EB675001DIP. The design uses a minimal number of additional components to achieve this display. The user CPLD is used to provide all control and timing logic reducing circuit complexity. More in depth information on composite video, associated circui
TV video output for the EB675001DIP - schematic

ts and techniques can be found across the web a useful resource is the epanorama list of links and Rickard GunGĀ©e video howto Monochrome composite video can be generated with a very simple method. By using two logic outputs and carefully selected resistor values the required voltage levels can be generated. Composite video in its most basic form consists of a voltage level between 0 and 1V, where 0 V is used for synchronization, 0. 3V is used as black level and 1V is used as a white level. Obviously almost any shade can be created by varying the voltage between the 0. 3 and 1V levels, however for the simple display presented here black and white will suffice. A video frame is made up from two fields of 312 scan lines displayed 25 times a second. For our purposes we will treat the odd and even fields as identical, this halves our vertical resolution but makes the design much simpler as we don`t have to do interlacing, effectively therefore we are producing 312 scan lines 50 times a second giving a line rate of 15, 600 lines per second (strictly speaking each frame has an additional line and the correct line rate is 15, 625 however the missing 25 lines will not prove problematic in practice). Each scan line lasts for 64 S and consists of a "front porch" of 2 S, a horizontal sync pulse of 4 S, a rear porch of 6 S and 52 S of displayed data. The diagram illustrates this along with a typical scan line waveform for some video...



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