micro - Principle of MicrocomputerUEE 2301/1142 Chap 10....

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Principle of Microcomputer Serial Port 1 Principle of Microcomputer UEE 2301/1142 Chap 10. MCS-51 Serial Port Operation 微算機原理與實驗 宋開泰 Office EE709 Phone 5731865 (校內分機: 31865 E-mail [email protected] URL http://isci.cn.nctu.edu.tw
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Principle of Microcomputer Serial Port 2 Serial Port Operation Outlines: • Serial I/O Protocols • Asynchronous Protocols • MCS-51 Serial Port Operation
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Principle of Microcomputer Serial Port 3 Terminal or Computer Data Terminal Equipment Modem Modem DTE Terminal or Computer Transmitter Receiver ( Phone line) Digital Data (Protocol is needed) Analog Data Digital Data DTE DCE DTE DCE System architecture of serial communication
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Principle of Microcomputer Serial Port 4 RS-232 Interface • DTE: Data Terminal Equipment • DCE: Data Communication Equipment • MODEM: Modulator/ Demodulator • RS-232 is a standard originally for providing a specification for connecting remote devices over the telephone networks through modems. Later (as now in wide use) it is used for terminal and equipment without using modems.
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Principle of Microcomputer Serial Port 5 RS-232 Signals Pin 2: TxD Transmit Data, transmits data from the DTE to DCE Pin 3: RxD Receive Data, transmits data from the DCE to DTE Pin 7: Signal Ground (Common) Pin 4: RTS* Request To Send, general purpose output Pin 5: CTS* Clear To Send, general purpose input Pin 6: DSR* Data Set Ready, general purpose input, to signal to the DTE that the DCE has been powered up and is ready to go Pin 20:DTR* Data Terminal Ready, general purpose output Pin 8 :DCD* Data Carrier Detect, on DTE, it is frequently used to disable data reception Pin 1: Shield Ground, if it is safe to connect the chassis ground together
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Principle of Microcomputer Serial Port 6 ASCII Code
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Principle of Microcomputer Serial Port 7 Asynchronous Protocols Electrical conventions: RS-232 • Timing convention : used frequency: 300, 600, …, 9600, 19200 = BAUD rate ↓↓ LSB MSB Idle or prior stop Start bit 7 data bits 1 parity bit One or two stop bits
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Principle of Microcomputer Serial Port 8 Asynchronous Protocols Least significant bit (LSB) first pattern (in time) ± 10000010 recognized as 01000001 = 41 H = “A” ASCII code Start and stop bit: identify the beginning and end of each transfer; permit a receiver to resynchronize a local clock to each character. Receiver samples bits at the center of the bit period, plus a good estimation of the leading transition on the start bit, plus both clocks to be accurate within 5 error margin (no problem with crystal clocks). To make the leading edge discoverable, the start bit is made different from both the idle state and the stop bits. Fast clock is used to determine the center of the star bit, 16 × clock time base.
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Principle of Microcomputer Serial Port 9 Asynchronous Protocols • Use a start and stop bit of opposite polarity → 20 overhead 8 bits 16 bits 16 bits 16 bits start bit
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Principle of Microcomputer Serial Port 10 Serial port clocking
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Principle of Microcomputer Serial Port 11 Parameters for setting up a serial port 1. The number of data bits/character 2. The number of stop bits 3. The parity bit 4. Baud rate
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Principle of Microcomputer Serial Port 12 Interfacing a PC and a Modem
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Principle of Microcomputer Serial Port 13 Null Modem Connection
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Principle of Microcomputer Serial Port 14 Examples of RS-232 Connection
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Principle of Microcomputer Serial Port 15 Logic Level of RS-232 and TTL Logic
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Principle of Microcomputer Serial Port 16 Serial link transceiver MAX232
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Principle of Microcomputer Serial Port 17 Serial link structure
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This note was uploaded on 01/11/2012 for the course ELECTRIC 101 taught by Professor Chen during the Spring '11 term at National Chiao Tung University.

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micro - Principle of MicrocomputerUEE 2301/1142 Chap 10....

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