Programmable data processing communications multiplexer

Abstract

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.