Physical Layer Programming - Slides (R1)

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

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SCI 232 CSCI 232 Computer Networking: Physical Layer Programming George Blankenship CSCI 232 - Programming George Blankenship 1
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Communication Environment h sical La er Physical Layer Interface Physical Layer Interface nvisible) (invisible) Computer Modem Telephone Telephone circuit Parallel/Serial Interface Link Layer Interface CSCI 232 - Programming George Blankenship 2
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Lecture Outline • Programming concepts – Device control evice status Device status • Win32 API (C++) • Javax Comm API CSCI 232 - Programming George Blankenship 3
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Basic Problem •Concepts hannels • Physical layer implemented in hardware –Channels –Programming hysical – Interface is a computer port ontrols and data use same port •Physical •Win32 API vax comm API Controls and data use same port • Control and data are separated by use of •javax.comm API –Basics isteners channels • Channels are separated by either events –Listeners –Events lasses or space –Classes –Extensions CSCI 232 - Programming George Blankenship 4
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Event Separated Channels •Concepts hannels • In-band signaling – Commands and data use same path (wires) ommands reduce user information band pass –Channels –Programming hysical – Commands reduce user information band pass • The current state (command/data) is etermined according to information that •Physical •Win32 API vax comm API determined according to information that preceded he keying information cannot be used as •javax.comm API –Basics isteners The keying information cannot be used as data or control information – The data pattern that signals “control information –Listeners –Events lasses follows” is not an available data pattern – The information encoding must be the same for control and data –Classes –Extensions CSCI 232 - Programming George Blankenship 5
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Space Separated Channels •Concepts hannels • Out-of-band signaling –Channels –Programming hysical – Commands and data use completely different paths (wires, time) •Physical •Win32 API vax comm API – No reduction in user information band pass • Command path can be used •javax.comm API –Basics isteners simultaneously with the data path – Encoding on the two paths is independent –Listeners –Events lasses – Synchronization of the two paths may be difficult –Classes –Extensions CSCI 232 - Programming George Blankenship 6
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I/O Programming •Concepts hannels • Two components to each I/O –Channels –Programming hysical – Recipient, waiting entity, device (write to device) – Generator, active entity, program (read from device) •Physical •Win32 API vax comm API • Device – Service provider ust wait for service request •javax.comm API –Basics isteners – Must wait for service request – State at beginning of session is unknown (to program) rogram –Listeners –Events lasses • Program – Requestor of service – Read/write are service request mechanism –Classes –Extensions CSCI 232 - Programming George Blankenship 7
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General Algorithm
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Physical Layer Programming - Slides (R1) - CSCI 232 CSCI...

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