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V.23 Modem TMS320C5000 DSP Code
Description:
implements the ITU Data Modem function V.23. This provides half-duplex
data transmission over 2 wires and full-duplex over 4 wires, at two rates,
one 1200b/s and the other 600b/s, over the telephone network. Also provided
(optionally) is a half-duplex backward channel of 75b/s which can be operated
independently of the main channel. Duplex channel separation is achieved
by band splitting. The assembler software is operated by callable subroutines,
eg for initialisation and for per-sample processing of input/output samples
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. A stripped down version is available for Caller
Identification (CID) use.
Interfaces:
at the sample interface, the code can operate at 8.0kHz and 9.6kHz sample
rates. At the data interface, operation can be in either Asynchronous
or Synchronous mode. In Asynchronous mode, data is transferred with start
& stop bits auto-inserted/-deleted. In Synchronous mode, data is transferred
transparently, with the receiver performing clock recovery on bit transitions.
In both cases, the data can be passed in multiple-bit blocks, and the
nominal clock used is 1200Hz or 600Hz.
At the control interface,
the assembler code has one 16-bit control word to sequence operation and
to set operating parameters such as data size, and one diagnostic word
to convey data transfer status such as ready-to-send and line-signal-detected.
With the C wrapper, control and diagnostics are provided by routine call
arguments and returned values.
Performance:
- SNR for 10-6 Error Rate on Flat Channel (4kHz BW noise): 1.2kb/s - 12.5dB; 0.6kb/s 8.5dB
Processor Load:
| Sample rate | MIPS# | Data memory (words) | Prog memory (bytes)# |
| 8.0kHz | 2.5(4.5) | 49(89) | 0.5k(0.9k) |
| 9.6kHz | 3.0(5.4) |
-
#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
