(64)--CH2-7-2 Working Principle of UAR嵌入式系统原理.ppt

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1、第第2 2章章 单片机原理与应用单片机原理与应用Principles Principles and Applications of and Applications of MicrocontrollerMicrocontrollerChapter 2.7 UART2.7.2 Working Principle of UART(1)Functions of UART interface:lGenerate Baud Rate;lTransfer Parallel data to serial format;lReceive serial bits to SBUF;lReceive&Transfe

2、r simultaneously.Chapter 2.7 UART2.7.2 Working Principle of UART(2)Generate Baud Rate The Baud Rate is determined by Oscillator and Timer1.Baud Rate=(T1 overflow rate)*2SMOD/32T1 overflow rate=(fosc/12)/(256-TH1)So if Baud rate is 1200bps and fosc=11.0592MHz,TH1 will be:256-TH1=(11059200/12)/(1200*3

3、2)TH1=232=E8(Hex)Chapter 2.7 UART2.7.2 Working Principle of UART(3)Serial Format Serial Format is determined by SCON Register.The bit 9 is in SCON,called TB8/RB8Chapter 2.7 UART2.7.2 Working Principle of UARTSM0SM0SM1SM1MODEMODEDESCRIPTIONDESCRIPTIONBAUD RATEBAUD RATE0008-bit Shift Register1/12 the

4、quartz frequency0118-bit UARTDetermined by the timer 11029-bit UART1/32 the quartz frequency(1/64 the quartz frequency)1139-bit UARTDetermined by the timer 1serial port mode Chapter 2.7 UART2.7.2 Working Principle of UARTMode 1-8-bit UARTSendReceiveTotal 10 bitsChapter 2.7 UART2.7.2 Working Principl

5、e of UART(4)Send/Receive byte Using SBUF to send or receive bytes.lThere are 2 SBUF registers physically.lWriting to SBUF one byte,the uart will send it to TXD pin in serial format.lOn the same time,uart can receive serial bits into another SBUF.We can call it receive SBUF.Reading from SBUF means read this register.