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V.32bis Data Pump Software for Texas TMS320C54x/C55x & C2xx/C5x DSPs

This software implements the ITU Data Modem function V.32bis, which provides full-duplex data transmission at rates of 14.4, 12, 9.6, 7.2, & 4.8kb/s over the telephone network. Included is backwards compatibility to V.32. Duplex channel separation is achieved by echo-cancelling for both land-based and satellite calls. Good error performance is assured by the use of trellis coding and adaptive equalisation. The software is in the form of two callable subroutines, one for initialisation and one for processing of input/output data and sample blocks. 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 in the ‘C54xC55x code version, so being re-entrant to facilitate the implementation of multiple modems on a single DSP. A comprehensive user's guide is provided with the code. Test results are available.

Interfaces: at the sample interface, the code can operate at 9.6kHz or 8.0kHz 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 sequences operations and sets parameters, and two diagnostic words convey data transfer and receiver status.

Performance: sophisticated techniques have been incorporated into the software to give excellent performance under noisy or poor line conditions. Over flat channels, near matched-filter performance is obtained. Over very severe channels such as the TAS Telephone Network Emulator ConUS Poor Voice channel - 30dB attenuation across the 3kHz band - the modem code will still operate at 14.4kb/s. 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 14.4kb/s: 22.0dB - Flat Channel ; 26.0dB - Bell 3002 Channel

DSP Load - C54x/C55x version: parameters given for operation at a 9.6kHz sample rate - operation at an 8.0kHz sample rate requires an extra 0.3MIPS, 20 data memory, and 0.2k program memory words:

• MIPS: 7.8

• Data memory: 3.1k# words

• Program memory: 6.0k words

DSP Load - C2xx/C5x version: operation at an 8.0kHz sample rate requires an extra 0.6MIPS, 30 data memory and 0.3k program memory words:

• MIPS: 8.6

• Data memory: 6.0k# words

• Program memory: 7.1k words

# covers 1.3secs. round-trip-delay

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