Home | Modem Data Pumps | Telephony | Audio | Utilities | Consultancy | Contact Us

V.27bis/ter Data Pump Software for Texas TMS320C54x/C55x & C2xx/C5x DSPs

This software implements the ITU Data Modem functions V.27bis & V.27ter, which provide half-duplex data transmission at rates of 4.8 & 2.4kb/s over the telephone network for applications such as Group 3 Fax. Also provided is full-duplex transmission for 4-wire leased line operation. An optional independently-controlled backward channel can be incorporated for rates of up to 75b/s. Good error performance is assured by the use of adaptive equalisation. The code features fast initial training & train-on-data - V.27bis, and fast resync - V.27ter. 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 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: over flat channels, near matched-filter performance is obtained.

SNR figures for 10^-6 error rate are:

• @ 4.8kb/s: 15.5dB - Flat Channel ; 17.0dB - Bell 3002 Channel

• @ 2.4kb/s: 9.0dB - Flat Channel ; 10.0dB - 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 - #denotes with backward channel:

• MIPS: 3.0(6.0#)

• Data memory: 235(290#) words

• Program memory: 2.5k(2.9k#) 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 words - #denotes with backward channel:

• MIPS: 3.4(6.3#)

• Data memory: 242(287#) words

• Program memory: 2.3k(2.8k#) words

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