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Asynchronous Serial Communication

Asynchronous Serial Communication. Peter Szyszko. Agenda. Serial Basics Async serial communication data format Async communication types RS-232 Essential FIB1-SRLM-SC002. Start. Data. Parity. Stop. 0. 5, 6, 7, 8. 1. 1, 1.5, 2. Unit: bit. Async Serial Communication Data Format.

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Asynchronous Serial Communication

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  1. Asynchronous Serial Communication Peter Szyszko

  2. Agenda • Serial Basics • Async serial communication data format • Async communication types • RS-232 Essential • FIB1-SRLM-SC002

  3. Start Data Parity Stop 0 5, 6, 7, 8 1 1, 1.5, 2 Unit: bit Async Serial CommunicationData Format • Start bit: Always fill “0” • Data bit: 5, 6, 7, 8 bit • Parity: None, Odd, Even, Space, Mark • Stop bit: 1, 1.5(Data bit =5), 2 bit • Data Frame Length If N, 8, 1: Data frame length is 10 bits. If E, 7, 2: Data frame length is 11 bits.

  4. Async Communication Types

  5. Start Start Data Data Parity Parity Stop Stop Stop Stop Parity Parity Data Data Start Start RS-232 signal definition 5V 0V +12V UART Transceiver D0 -12V …… Tx D7 Rx 5V 0V Parallel +12V TTL RS-232 -12V

  6. RS-232 Connection Type - I • Example: PC + Null Modem cable + PC • RS-232 Signals • Short DCD with DSR to ensure all type of software works. Such as serial console port on rack server. DTE Signals Wiring DTE Signals TxD RxD RTS CTS DTR DSR DCD GND TxD RxD RTS CTS DTR DSR DCD GND

  7. RS-232 Connection Type - II • Example: PC + Straight cable + Modem • RS-232 Signals • DCD on DCE device is generally an output signal DTE Signals Wiring DCE Signals TxD RxD RTS CTS DTR DSR DCD GND RxD TxD CTS RTS DSR DTR DCD GND

  8. H/W Flow Control PC 2 PC 1 * RTS stop to transmit data.

  9. S/W Flow Control 1. Xon Rx Tx PC 1 PC 2 3. Xoff 2. Start to Send Tx Rx X 4. Stop to send

  10. Flow Control Comparison

  11. 3-Wire RS-232 Wiring Site A Signal Site B Signal ================================== Tx --------------------------- Rx Rx --------------------------- Tx GND -------------------------- GND

  12. 8-Wire RS-232 Wiring Site A Signal Site B Signal ================================== Tx --------------------------- Rx Rx --------------------------- Tx RTS --------------------------- CTS CTS --------------------------- RTS DTR -------------------------- DSR DSR -------------------------- DTR DCD -------------------------- DCD GND -------------------------- GND

  13. 8-Wire RS-232 Wiring

  14. 3-Wire vs. 8-Wire

  15. Transmission Distance • Distance -- EIA Standard / Real World Performance

  16. FIB1-SRLM-SC002

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