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V.29 Modem TMS320C5000 DSP Code

Description: implements the ITU Data Modem function V.29, which provides full-duplex data transmission at rates of 9.6, 7.2, & 4.8kb/s over 4-wire leased lines. The software also allows half-duplex transmission over the telephone network for application with Group 3 Fax. Good error performance is assured by the use of adaptive equalisation. The assembler software is in the form of callable subroutines, eg for initialisation and for main-routine processing of input/output sample blocks and data. The user is responsible for interfacing samples and data to hardware.
         In the assembler interface, the code is re-entrant to facilitate multi-channel operation. A C-callable wrapper can also be provided, allowing individual channels to be called from C to process multiple sample blocks. A comprehensive user's guide together with example application files are provided with the code. Test results are available.

Interfaces: at the sample interface, the code can operate at 8.0kHz and 9.6kHz sample rates. Transmit and receive samples are transferred on a common clock, to which the transmit clock is synchronised. The receive clock is interpolated in the DSP code for synchronisation to the far-end modem. At the data interface, data is transferred in buffers under pointer control.
         At the control interface, the assembler code has one 16-bit control word to sequence operation and to set operating parameters, and two diagnostic words to convey data transfer status and signal quality. With the C wrapper, control and diagnostics are provided by routine call arguments and returned values.

Performance: over flat channels, near matched-filter performance is obtained. SNR for 10-6 Error Rate (Flat Channel - 4kHz BW noise):

• 9.6kb/s - 20dB; 7.2kb/s - 16dB; 4.8kb/s 12dB
  

Processor Load:

- #figures are for TMS320C54x operation with the assembler interface

Availability: NOW - sale is under licence - integration support offered