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Sharp QA-1650 Service Manual
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9.5.Computer signal automatic IdentificationThis function distinguishes the video signal from the computer connected to the QA-1650, and automatically ad-justs input timing in IC2(M.P.U.).The following signals (1)~(4) are sent from IC1 to IC2 to enable IC2 to perform the automatic indentification.(1)VSC(IC1,pin 11)Itis the vertical synchronizing signal of the video signal from the connected computer.IC2 measures the periodof this signal.(2)VPOL(IC1,pin 10)It indicates the polarity of the vertical synchronizing signal of the video signal from the connected computer.(3)F256HS(IC1 pin 9)It is the horizontal synchronizing signal of the video signal from the connected computer,divided by 256.IC2 measures the period of this signal.(4)HPOL(IC1 pin 8)It indicates the polarity of the horizontal synchronizing signal of the video signal from the connected computer.IC2 identifies the type of computer from above information (1)~(4) and writes the parameters into the registers onIC1 for automatic setting.Identifying of no connection:If F256HS signal remains unchanged for a certain period(approximately 130ms),IC2 identifies "no connection",turns both VCOH and VCOL to "L" level to stop VCO function,and displays demonstration picture.vcoO| | SELECTz Routine =IC3 SettinJudgementHSYNC HSYNC Polarity RoutineJudge CircuitH.period1/256 Devide Measure= Pi oeA—784 V.periodosMeasureRoutiVSYNCPolarity40outineJudgeCircuit1635 |
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