Digital multi-customer data interface

Abstract

A communication method and digital multi-customer data interface for interconnecting a number of customer terminals to a main packet switching network of a local area data transport system that provides data communication services such as interactive video text service between data service vendors and customers. The digital multi-customer interface utilizes a main processor, control circuit, and multi-customer protocol controller to implement the protocol functions for the communication of packets and control information over individual serial transmission paths. The multi-customer protocol controller comprises a control processor and a formatter circuit for synchronously communicating packets for a plurality of customer terminals via customer line units and customer lines. The control processor performs byte-to-packet and packet-to-byte functions between the main processor and the formatter circuit. The formatter circuit is shared in common by all of the customer lines and performs the functions of assembling and disassembling data bytes from and to individual data bit signals, performing error cyclic redundancy checks and generations, performing flag recognition and generations, and performing bit stuffing and unstuffing. The control circuit handles communication of all control and status information between the main processor and the customer line units. The control buffer periodically transmits the control information received from the main processor to all of the customer units and receives back from them status information which is stored for later use by the main processor.