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V.26bis Modem TMS320C5000 DSP Code
Description:
implements the ITU Data Modem functions V.26bis & V.26, which provide
data transmission at rates of 2.4 & 1.2kb/s in half-duplex over the
telephone network and full-duplex 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. 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.
In the assembler interface, the
code is re-entrant to facilitate multi-channel operation. A C-callable
wrapper can also be provided, allowing individual channels to be called
from C to process multiple sample blocks. A comprehensive user's guide
together with example application files are 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, the assembler
code has one 16-bit control word to sequence operation and to set operating
parameters, and two diagnostic words to convey data transfer status and
signal quality. With the C wrapper, control and diagnostics are provided
by routine call arguments and returned values.
Performance: over flat channels, near matched-filter performance is obtained. SNR for 10-6 Error Rate (4kHz BW noise):
- 2.4kb/s: 8.5dB Flat Channel; 11.5dB Bell 3002 Channel
- 1.2kb/s:
5.5dB Flat Channel; 8dB Bell 3002 Channel
Processor Load:
| Sample rate | MIPS# | Data memory (words) | Prog memory (bytes)# |
| 8.0kHz | 1.8(3.6) | 170(210) | 1.7k(2.1k) |
| 9.6kHz | 1.5(3.6) | 150(190) | 1.5k(1.9k) |
-
#figures are for TMS320C54x operation with the assembler interface
- figures in ( ) are with the backwards channel
Availability: NOW - sale is under licence - integration support offered
