AlgoTron DSP
Software for Telecoms & Audio
a TI DSP Third Party Network
Member
Home
Modems
Telephony
Audio
Utilities
Consultancy
Glossary
Index
Contact
us
V.22bis Modem TMS320C5000 DSP Code
Description:
implements the ITU Data Modem functions V.22bis and V.22, which provide
full-duplex data transmission at rates of 2.4, 1.2, & 0.6kb/s over
the telephone network. The code can also send the V.25 2100Hz auto-answer
signal. Duplex channel separation is achieved by band splitting with 1200Hz
and 2400Hz carriers for each channel. An (optional) 1800Hz guard tone
is sent in the high channel. Good error performance is assured by the
use of adaptive equalisation. 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: near matched-filter performance is obtained over both flat and very severe channels. SNR for 10-6 Error Rate (4kHz BW noise):
- 2.4kb/s:13.5dB - Flat Channel; 14.0dB - Bell 3002 Channel
- 1.2kb/s: 6.5dB - Flat Channel; 7.5dB - Bell 3002 Channel
- 0.6kb/s:
3.5dB - Flat Channel; 4.5dB - Bell 3002 Channel
Processor Load:
| Sample rate | MIPS# | Data memory (words) | Prog memory (bytes)# |
| 8.0kHz | 3.6(3.5) | 244 | 2.6k(2.4k) |
| 9.6kHz | 3.2(3.1) | 224 | 2.4k(2.2k) |
-
#figures are for TMS320C54x operation with the assembler interface
including Remote Digital Loop
- figures in ( ) for
V.22-only ie 1.2-0.6kb/s
Availability: NOW - sale is under licence - integration support offered
