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V.17 Data Pump Software for Texas TMS320C54x/C55x & C2xx/C5x DSPs

This software implements the ITU Data Modem function V.17, which provides half-duplex data transmission at rates of 14.4, 12, 9.6, & 7.2kb/s over the telephone network for use in Group 3 Fax equipment. Good error performance is assured by the use of trellis coding and adaptive equalisation. A fast-train algorithm is implemented for resynchronisation after initial training. 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 version, so the code re-entrant for implementing 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 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 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.

• 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:

• MIPS: 5.3

• Data memory: 450 words

• Program memory: 3.7k words

DSP Load - 'C2xx/'C5x version: parameters given for operation at a 9.6kHz sample rate - operation at an 8.0kHz sample rate requires an extra 0.6MIPs, 30 data memory and 0.3k program memory:

• MIPS: 5.4

• Data memory: 441 words

• Program memory: 4.7k words

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