Part # Application Note Television ST92196A ST92T196 8-bit MCU for TV AN1841 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: Closed Caption and XDS Software for the ST92x196 family


Part Details:

AN1841 APPLICATION NOTE Closed Caption and XDS Software 1 INTRODUCTIONThis document describes the Closed Caption and eXtended Data Service (XDS) extractionsoftware module available for the ST92x196 family. 2 COMPOSITE VIDEO SIGNAL 2.1 Introduction The composite video signal waveform is the amplitude-versus-time representation of the sig-nal produced jointly by the television camera, the camera-control unit, the synchro generatorand, for color operation, the color encoder. Signals considered in this chapter apply to the 525-line NTSC color television system used in the USA. 2.2 Characteristics Picture scan, is from left to right and top to bottom, consisting of 525 horizontal lines per frameand 30 frames per second. Each frame is divided into two alternating fields. The polarity ofmodulation is negative. 70% of the amplitude range is selected to transmit the brightness in-formation. The 30% left are available for the synchronizing information, needed to lock the pic-ture beam to the camera or other source. In color television transmissions, two synchronizationsignals are used to control deflection, a third one provides the color-coding information. Obsolete Product(s) - Obsolete Product(s) Rev. 2 AN1841/0704 1/17 AN1841 - APPLICATION NOTE 2.2.1 Horizontal synchro The horizontal synchro is used to blank the source output during the horizontal retrace intervaltime. Line frequency = 59.94 Hz/2 x 525 lines = 15734 Hz Figure 1. Horizontal synchro HORIZONTAL BLANKING BLANKING LEVEL PROGRAM COLOR BURST HORIZONTAL SYNCHRO Obsolete Product(s) - Obsolete Product(s) 2/17 AN1841 - APPLICATION NOTE 2.2.2 Vertical synchro The vertical synchro is used to blank the source output during the vertical retrace interval time.Also, in order to respect a good interlace, signals are different on two successive fields. In onecase the last horizontal pulse is one half-line period preceding the vertical blanking interval,and in the next field, the last horizontal pulse will followed by a full line period. Vertical synchro-nizing is guaranteed by doubling the horizontal pulse frequency during the vertical retrace. Figure 2. Vertical synchro FIELD 1 VERTICAL BLANKING INTERVAL 3 LINES 3 LINES 3 LINES PRE-EQUALIZING VERTICAL SYNCHRO POST-EQUALIZING LINE 21 FIELD 2 VERTICAL BLANKING INTERVAL 3 LINES 3 LINES 3 LINES PRE-EQUALIZING VERTICAL SYNCHRO POST-EQUALIZING LINE 21 2.2.3 Color synchro The third synchro signal is the color-synchronizing burst which gives the reference phase forthe chrominance subcarrier. The synchronizing information is contained in a short burst of thesubcarrier frequency which follows the horizontal pulse and is completed before the start ofthe picture modulation. Obsolete Product(s) - Obsolete Product(s) 3/17


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Application Note Television ST92196A ST92T196 8-bit MCU for TV AN1841.pdf Datasheet