US 4,409,656 A · Serial data bus communication system

Abstract

A node device for use in a digital data processing and communications system of the type utilizing a bus organization for facilitating the interconnection of a large plurality of digital data processing devices (user devices) in which redundant cables are employed. The node devices are interposed between the user devices and the redundant cables to permit automatic reconfiguration of the interconnection of the user devices in the event of malfunctioning or severing of one or more of the cable sets within a minimum period of time. The node devices provide the user devices with the structure needed to detect and diagnose system problems and to effect recovery procedures. In accordance with the invention, one of the plurality of nodes functions as the Bus Controller and by sampling the remaining nodes in the system, it determines the priority with which user devices may transmit or receive data over the bus. Each of the nodes employed is substantially identical and any one may be selected to function as the Bus Controller. Each includes a Microprogrammed Controller and necessary firmware to permit the controller to function in conjunction with special purpose hardware including a Programmable Logic Array (PLA) configured to perform a pre-processing function on control line inputs so that poll/response traffic on the active cables can continue with a minimum of delay.

Claims25

Dependent claims

In a serial data bus transmission system of the type used to interconnect a plurality of user devices for message intercommunication over transmission cables, said system including a plurality of cables, one of which acts as an active control cable and one of which acts as an active message cable at a given time, with at least one bus access module coupled to each of said plurality of cables, a plurality of node devices for coupling said user devices to said bus access modules, each of said node devices comprising in combination:

(a) bus input/output means including data format conversion means coupled to said bus access modules for selecting said active ones of said control cable and said message cable and for transmitting or receiving digital messages and control signals therethrough;
(b) a control bus coupled to said bus input/output means;
(c) a message bus coupled to said bus input/output means;
(d) control line sequencer means coupled to said control bus for receiving control signals therefrom and including logic means for performing preprocessing functions relative to said control signals for determining whether said control signals are intended to affect that node device and are of a proper format;
(e) controller means adapted to receive preprocessed data signals from said control line sequencer and to develop command signals in accordance with said preprocessed data signals, and further status indicators;
(f) means including said control bus and said bus input/output means for sending said command signals on said active control cables to other of said plurality of nodes coupled to said active control cable;
and
(g) means responsive to said command signals for controlling the flow of messages over said message bus and between said plurality of user devices.

5 more elements

Dependencies are inferred from the claim text.

Serial data bus communication system

Life of this patent

Serial data bus communication system

Life of this patent

Abstract

Claims25