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CH7007A Datasheet(PDF) 6 Page - List of Unclassifed Manufacturers |
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6 / 49 page CHRONTEL CH7007A 6 201-0000-002 Rev. 2.7, 08/23/2000 Digital Video Interface The CH7007 digital video interface provides a flexible digital interface between a computer graphics controller and the TV encoder IC forming the ideal quality/cost configuration for performing the TV-output function. This digital interface consists of up to 12 data signals and 4 control signals, all of which are subject to programmable control through the CH7007 register set. This interface can be configured as 8 or 12-bit inputs operating in multiplexed mode. It will also accept either YCrCb or RGB (15, 16 or 24-bit color depth) data formats and will accept both non-interlaced and interlaced data formats. A summary of the input data format modes is as follows: The clock and timing signals used to latch and process the incoming pixel data is dependent upon the clock mode. The CH7007 can operate in either master (the CH7007 generates a pixel frequency which is either returned as a phase-aligned pixel clock or used directly to latch data), or slave mode (the graphics chip generates the pixel clock). The pixel clock frequency will change depending upon the active image size (e.g., 640x480 or 800x600), the desired output format (NTSC or PAL), and the amount of scaling desired. The pixel clock may be requested to be 1X, 2X or 3X the pixel data rate (subject to a 100MHz frequency limitation). In the case of a 1X pixel clock the CH7007 will automatically use both clock edges, if a multiplexed data format is selected. Sync Signals: Horizontal and vertical sync signals will normally be supplied by the VGA controller, but may be selected to be generated by the CH7007. In the case of CCIR656 style input (IDF = 9), embedded sync may also be used. In each case, the period of the horizontal sync should be equal to the duration of the pixel clock, times the first value of the (Total Pixels/line x Total Lines/Frame) column of Table13 on page 29 (Display Mode Register 00H description). The leading edge of the horizontal sync is used to determine the start of each line. The Vertical sync signal must be able to be set to the second value in the (Total Pixels/Line x Total Lines/Frame) column of Table13 on page 29. Master Clock Mode: The CH7007 generates a clock signal (output at the P-OUT pin) which will be used by the VGA controller as a frequency reference. The VGA controller will then generate a clock signal which will be input via the XCLK input. This incoming signal will be used to latch (and de-multiplex, if required) incoming data. The XCLK input clock rate must match the input data rate, and the P-OUT clock can be requested to be 1X, 2X or 3X the pixel data rate. As an alternative, the P-OUT clock signal can also be used as the input clock signal (connected directly to the XCLK input) to latch the incoming data. If this mode is used, the incoming data must meet setup and hold times with respect to the XCLK input (with the only internal adjustment being XCLK polarity). Slave Clock Mode: The VGA controller will generate a clock which will be input to the XCLK pin (no clock signal will be output on the P-OUT pin). This signal must match the input data rate, must occur at 1X, 2X or 3X the pixel data rate, and will be used to latch (and de-multiplex if required) incoming data. Also, the graphics IC transmits back to the TV encoder the horizontal and vertical timing signals, and pixel data, each of which must meet the specified setup and hold times with respect to the pixel clock. Pixel Data: Active pixel data will be expected after a programmable number pixels times the multiplex rate after the leading edge of Horizontal Sync. In other words, specifying the horizontal back porch value (as a pixel count), plus horizontal sync width, will determine when the chip will begin to sample pixels. Table 2. Input Data Formats Bus Width Transfer Mode Color Space and Depth Format Reference 8-bit 2X-multiplexed RGB 15-bit 5-5-5 over two bytes 8-bit 2X-multiplexed RGB 16-bit 5-6-5 over two bytes 8-bit 2X-multiplexed YCrCb (24-bit) Cb,Y0,Cr,Y1,(CCIR656 style) 12-bit 2X-multiplexed RGB 24 8-8-8 over two words - ‘C’ version 12-bit 2X-multiplexed RGB 24 8-8-8 over two words - ‘I’ version |
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