Software for Telecoms & Audio
V.27 Modem TMS320C5000 DSP Code
implements the data pump function of the ITU Modems 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.
In both cases, 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 train-on-data (V.27bis)
& fast resync. (V.27ter) from initial training. 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.
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.
Performance: over flat channels, near matched-filter performance is obtained. SNR for 10-6 Error Rate (4kHz BW noise):
#figures are for TMS320C54x operation with the assembler interface
Availability: NOW - sale is under licence - integration support offered