Publication Date


Document Type


First Advisor

Tahernezhadi, Mansour

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering


Computer network protocols; Telecommunication--Message processing; Modems


In this thesis we implement a message protocol stack to be useful in modems. After designing the functionality of the protocol, the implementation was written. This is a platform independent code written in ?C? language. This code can be compiled by any DSP compiler to get that DSP specific object code.The protocol code need not reside on the DSP. The call progress and other functionalities can all run on the DSP along with the protocol stack. Alternatively, if the architecture consists of a microcontroller and a DSP, the DSP can run the call progress and data pump code and the protocol can reside on the microcontroller. The important portion of the code now runs as 5 state machines. There are 5 ?C? files which define the state machines.The remaining files are supporting files which define functions of different types to manipulate data while in specific states so as to bring about state changes and data manipulation. The state machines and individual functions are described later. The protocol can be used to send both voice as well as data. The protocol can be in Message protocol mode or Modem or Fax mode. The DCE which originates the switch to data mode can send a start tone and mode indicator to switch from voice to data mode. We can then transmit pictures or drawings. We also have the modem and fax functionalities. Before any exchanges, both the DCEs exchange capabilities with each other. The capability exchange can be 1 way or both ways. The data between the two modems is sent in HDLC format. This consists of a flag, address, control, information, checksum, and another flag. The control information is split up into control 1 and control2 bytes. The information, supervisory and unnumbered type frames are used in data exchange.


Includes bibliographical references (pages [92]-95)


ix, 99 pages




Northern Illinois University

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