L3LocalAsync6 - Part 1 Data Transmission Part 1 Data...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Part 1 – Data Transmission Local Asynchronous Communication: RS-232 and USB Gail Hopkins Part 1 – Data Transmission Introduction ± Using electric current to transmit bits over short distances ± Present two mechanisms for sending characters over short distances Ð RS-232 Ð USB ± Baud rate and bandwidth ± Nyquist Sampling Theorem & Shannon’s Theorem Part 1 – Data Transmission Asynchronous Communication ± Where the receiver does not know when the sender will transmit Ð transmit when data are ready Ð variable delays between transmissions Ð no sender-receiver coordination beforehand ± E.g., keyboard connected to a computer ± Technically, the electrical signal does not contain information about where individual bits begin and end Using Electric Current to Send Bits ± Use a wire to create a circuit between the sender and receiver ± Negative voltage on the wire could represent a 1 and positive a 0 ± Waveform diagram shows variable delay Part 1 – Data Transmission Part 1 – Data Transmission Communication Standards ± Standards ensure that hardware from different vendors can inter-operate Ð Voltages used, length of time a voltage should be held, how rapidly the voltage should change ± Scope of “physical layer” standards Ð Mechanical Ð Electrical Ð Functional Ð Procedural ± Standards are published by standards organisations - ITU, ISO etc. Part 1 – Data Transmission The RS-232 Standard ± To connect keyboards, terminals etc. to computers over copper wire ± Concerned with 7-bit characters ± Details of physical connection (maximum length, plugs and sockets) ± Electrical details (voltages) ± Serial communication ± Asynchronous (for each character)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Part 1 – Data Transmission Example RS-232 Waveform Part 1 – Data Transmission RS-232 ± Never leaves 0 volts on the wire - an idle line is the same as a 1 bit ± Sender and receiver agree how long a bit lasts - receiver uses a local timer ± A 0 start bit signifies the start of a character and is followed by 7 data bits ± A minimum gap of 1 bit between characters (a phantom stop bit of 1)
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 6

L3LocalAsync6 - Part 1 Data Transmission Part 1 Data...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online