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V.61 Data Pump Software for Texas TMS320C54x/C55x DSPs

This software implements the ITU Data Modem function V.61. This operates in two full-duplex modes over the telephone network: audio+data for Simultaneous Voice Data (SVD) where the data rate is 4.8kb/s, and data-only for rates of 14.4, 12, 9.6, 7.2, & 4.8kb/s. In the data-only mode, an auxiliary channel of up to 343b/s is available.

Operation can be switched at the user interface during data mode and can be independent in each direction, though both ends send at the same rate in data-only mode. Duplex channel separation is achieved by echo-cancelling for both land-based and satellite calls. Good error performance is assured by the use of adaptive equalisation. The software is in the form of two callable subroutines, one for initialisation and one for processing of input/output line/audio sample blocks and data buffers.

The user is responsible for interfacing sample and data input & output to hardware. By making multiple sub-routine calls, the code can operate on blocks of samples. Data memory is offset-addressed, so making the code re-entrant and suitable for implementing multiple modems per DSP. A comprehensive user's guide is supplied 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, one 16-bit control word is used to sequence operation and to set operating parameters, and two diagnostic words convey data transfer status and signal quality.

Performance: over flat channels, near matched-filter performance is obtained. The software can automatically set the data rate according to line conditions and can renegotiate the data rate during data transmission as conditions change to maintain good throughput/error performance. The decision criteria can be adjusted at the user interface.

• SNR for 10^-6 error rate at data-only 14.4kb/s (4kHz BW noise): 26.0dB Flat Channel
  

DSP Load:

• MIPS: 15.0 (both 8.0 & 9.6kHz s.r.)

• Data memory: 6.4k words (for 1.3secs. RTD)

• Program memory: 6.1k words

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