Nasser H-Ali , Ashor _Alsellami
Computer Engineering Department-Faculty of Eng -.Al-fateh University
In the past few years high-speed data transmission over dialed telephone connection or over
leased lines has growth rapidly.
In this paper a versatile, high speed structure modem was designed .It permits the implementation
of several modulation formats with various speed options from the common TMS320C25 single
chip microprocessor which is controlled by a stored algorithms.
The TMS32C25 on-chip microprocessor can be programmed to produce either a phase or
frequency modulated synchronous signal and to demodulate it.
Using such a single chip signal processor as a basic building block, a low cost, high-speed
modem can be programmed to operate over unconditional lines.
The implemented modem operates at 1200 symbol/sec, with two bits per symbol (2400pbs using
DQPSK or with three bits per symbol (4800 pbs) using 8DPSK,and finally four bits per symbol
(9600 pbs) using D-16QAM with externally carrier recovery.
A series of processing cycle tactics was used to allow the microprocessor like TMS320C25 or
other DSP processors to handle all modem functions in real time. The microprocessor-based
modem is extremely flexible because its software controlled nature, and through programming it
will provide a Varity of additional functions. The system was tested in the case of perfect and