International Business Machines Corporation

Jan W Van Den Berg

Gordon Taylor Davis

Baiju Dhirajlal Mandalia

David Curtis Van Voorhis

Oscar E Ortega

William R Robinson, Jr

Douglas M O'Neal

Robert E Landa

David C Wu

Donald V Wildes

Leo A Sharp, Jr

Paul W Petroskey

Rafael J Picon

Dennis M Nagel

Roland J Millas

Richard H Robinson

Michael G Ho Lung

Loran R Queen

A dual digital signal processor (DSP) provides real time links between multiple time division channels of a digital carrier system (e.g. T-1) and a host data processor. Operating only on digital signals, internally and at its interfaces to the carrier and host systems, the DSP exchanges data and control signalling information with the carrier system and data and control information with the most processor, converting the data in passage to different digital forms. At the interface to the carrier system, signals are received and transmitted in a form adapted to diverse terminal equipment of users remotely linked to the carrier system via the switched public network. At the host interface, signals are transferred and received in a form suited to the data process requirements of the host system (e.g. data bytes directly representing alphanumeric characters). Thus, the DSP acts as the equivalent of multiple different types of modems in performing required conversions. The DSP may also perform processing services in order to reduce the processing burden on the host system (e.g. parity checking of data, detection of specific character functions in data or specific tones in audio signals, selective routing of voice to host storage for voice mail applications, etc.).

Real-time digital signal processing relative to multiple digital

A special purpose communications protocol processor (CPP) provides more efficient processing of layered communications protocols--e.g. SNA (Systems Network Architecture) and OSI (Open Systems Interconnection)--than contemporary general purpose processors, permitting hitherto unavailable operations relative to high speed communication links. The CPP contains special-purpose circuits dedicated to quick performance (e.g. single machine cycle execution) of functions needed to process header and frame information, such functions and information being of the sort repeatedly encountered in all protocol layers, and uses instructions architected to operate these circuits. The header processing functions given special treatment in this manner include priority branch determination functions, register bit reshaping (rearranging) functions, and instruction address processing functions. Frame processing functions so handled include CRC (cyclic redundancy check) computations, bit insertion/deletion operations and special character detection operations.

Specialized communications processor for layered protocols

A micro processor controlled user programmable communications multiplexer subsystem (herein referred to by the symbol PCS) capable of transmitting and receiving data on any one or more of 32 communications lines simultaneously. Each line may be dynamically assigned to a variety of communication characteristics, such as line speeds, character lengths, synchronous, or asynchronous operation, and code structures as well as protocol selections. The system of the invention provides the capability for the user to write his communications programs using novel operations commands that provide code structure and protocol independence as well as communication line independence. Various hardware features and queuing techniques are employed in order to maintain high transmission rates. Variable line scanning in the Teleprocessing Time Division Multiplexer of the PCS is programmably permissible; i.e., the time base for line scanning is fixed and is a multiple of the communication line rate, although the actual line to be scanned is programmably variable. The program ability is provided by a continuously scanned storage array which contains physical line addresses of the time division multiplexer. The scanning mechanism, while running, prioritizes the transmit buffer servicing of the individual lines.

Programmable communications subsystem

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Boca Raton, FL, United States of America

Jan W Van Den Berg