Physical Layer Programming (R1)

Physical Layer Programming (R1) - CSCI 232 - Computer...

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CSCI 232 - Computer Networking Physical Layer Programming George Blankenship 1 CSCI 232 - Programming George Blankenship 1 CSCI 232 Computer Networking: Physical Layer Programming George Blankenship CSCI 232 - Programming George Blankenship 2 Communication Environment Computer Modem Telephone Telephone circuit Parallel/Serial Interface Physical Layer Interface Link Layer Interface Physical Layer Interface (invisible) CSCI 232 - Programming George Blankenship 3 Lecture Outline • Programming concepts – Device control – Device status • Win32 API (C++) • Javax Comm API
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CSCI 232 - Computer Networking Physical Layer Programming George Blankenship 2 CSCI 232 - Programming George Blankenship 4 Basic Problem • Physical layer implemented in hardware – Interface is a computer port – Controls and data use same port • Control and data are separated by use of channels • Channels are separated by either events or space •Concepts –Channels –Programming •Physical •Win32 API •javax.comm API –Basics –Listeners –Events –Classes –Extensions CSCI 232 - Programming George Blankenship 5 Event Separated Channels • In-band signaling – Commands and data use same path (wires) – Commands reduce user information band pass • The current state (command/data) is determined according to information that preceded • The keying information cannot be used as data or control information – The data pattern that signals “control information follows” is not an available data pattern – The information encoding must be the same for control and data •Concepts –Channels –Programming •Physical •Win32 API •javax.comm API –Basics –Listeners –Events –Classes –Extensions CSCI 232 - Programming George Blankenship 6 Space Separated Channels • Out-of-band signaling – Commands and data use completely different paths (wires, time) – No reduction in user information band pass • Command path can be used simultaneously with the data path – Encoding on the two paths is independent – Synchronization of the two paths may be difficult •Concepts –Channels –Programming •Physical •Win32 API •javax.comm API –Basics –Listeners –Events –Classes –Extensions
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CSCI 232 - Computer Networking Physical Layer Programming George Blankenship 3 CSCI 232 - Programming George Blankenship 7 I/O Programming • Two components to each I/O – Recipient, waiting entity, device (write to device) – Generator, active entity, program (read from device) • Device – Service provider – Must wait for service request – State at beginning of session is unknown (to program) • Program – Requestor of service – Read/write are service request mechanism •Concepts –Channels –Programming •Physical •Win32 API •javax.comm API –Basics –Listeners –Events –Classes –Extensions CSCI 232 - Programming George Blankenship 8 General Algorithm • Control sent on control path • Control response received on control path
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This note was uploaded on 09/03/2010 for the course CS 232 taught by Professor Susan during the Summer '09 term at GWU.

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Physical Layer Programming (R1) - CSCI 232 - Computer...

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