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Call Waiting Caller ID (Standard) Detector TMS320C5000 DSP Code
Description: implements the landline telephony function of Call Waiting Caller IDentity (CWCID) generation. CWCID is sent off-hook in an established call to pass the identity of a third party trying to call one of the talking parties. The talking party can then accept the call by a hook-flash. CWCID is signalled from the exchange - the Generator end - by an alerting dual-tone signal CAS, and acknowledged by the subscriber - the Detector end - with another dual-tone signal ACK. The Caller ID message bytes are then sent by V.23 or Bell 202 modem modulation, formatted as in on-hook Caller ID. The CWCID Detector is for "standard" locales - eg ETSI, UK SIN 227, US Bellcore SDMF/MDMF, Bell Canada - but not for Japan. The software function summary is:
CWCID Detector: on detecting CAS it sends ACK, then demodulates the Caller ID data verified against the checksum, using the on-hook CID decoder routine. The Detector returns diagnostics, signalling CAS-detected for voice-blocking, then full message reception, or else failure due eg a CRC error.
The Detector forms
a buffer of the complete message data for the user interface in parameterised
byte form, excluding the checksum byte. Message de-parameterisation in
the user code gives flexibility in dealing with Caller ID categories.
The message buffer format is 2 per 16-bit word for efficiency in multi-channel
use.
The
Detector has an initialisation routine and a per-sample main routine and
is re-entrant with memory offset-addressing for multi-channel operation.
As well as from assembler, the routines can also be called from C, wrappers
being provided. The C main routine enables multiple sample blocks to be
processed. Sample rates of 8.0kHz and 9.6kHz can be set. A comprehensive
user's guide is provided with the code.
CAS detector performance:
| False detections: | 1 in ~4.5hours speech |
| Missed detections: | 1 in ~40000 CAS signals + speech |
Detector
data receiver performance:
| SNR for 10-6 BER on Flat Channel: | 12.0dB - Bell 202 ; 12.5dB - V.23 (4kHz BW noise) |
| Local loop line length for no errors: | >9km |
Processor Load:
| Function | MIPS# | Data memory (words) | Prog memory (words)# |
| CWCID-S Detector (+ CID Decoder/Rx) | 1.44 | (28 + M) x N | 547 |
-
#figures are for TMS320C54x operation with the assembler interface at
8.0kHz sampling
- in data memory figures M is the user-set buffer size at 2 bytes per
word and N is no. of channels
Availability: NOW - sale is under licence - integration support offered
