A digital signal processor yields enhanced data/FAX pump

摘要

The recent introduction of powerful special purpose semiconductor digital signal processing (DSP) circuits allows the implementation of complex and high performance communications functions. Specifically, the integration of such DSP circuits provides high speed communications capabilities to workstations and personal computers (PCs) for communication across the public switching telephone network (PSTN). The Motorola DSP56000 and DSP56300 family members of DSP circuits, designed as V.34 Plus data/V.17 fax/voice data pump modems, efficiently implement such functions. A data pump is a self-contained function block implemented with a combination of DSP circuitry and internal memory, that requires an analog front end and an external processor for control, but no additional user software programming is required. The data pump is responsible for the signal modulation and demodulation, coding, low level training, line equalization, echo canceling and the many other layer one (and part of layer two) functions such as those required by the V.34 Plus data modem and V.17 fax standards. By the simple addition of a DSP data/fax/voice pump, workstations and PCs can communicate with data resources such as electronic mail systems, bulletin boards, public data bases, Internet Service Providers (ISPs), corporate data bases, distant local area networks (LANs) and other PCs. Workstations and PCs now not only have the ability to be linked via a high speed V.34 Plus telephone modem but also provide many additional functions such as a telephone dialer, a telephone answering machine, a hands-free speakerphone, and a facsimile machine amongst others. Further, users can implement a direct digital modem (DDM) efficiently connecting an Integrated Services Digital Networks Services (ISDN) terminal adapter (TA) either to a far-end ISDN TA, or an analog modem which normally requires significant and complex circuitry. Similarly, the implementation of a "modem pool" is now implemented in a cost effective manner at ISPs and enterprise central sites. This paper examines and suggests solutions in the employment of advanced DSP circuits to provide cost effective and versatile data/fax pumps platforms for remote access for single users applications,and multichannel data/fax pumps serving enterprise network servers and ISPs applications.