Patent ID: 7861110

Claim:
A fault-tolerant communication system for communication between a control module and a processing module, wherein the control module and the processing module are each designed to be connected to a single RS-485 bus, said fault-tolerant communication system enabling the control module and the processing module to selectively communicate via at least two redundant half-duplex, multipoint, differential RS-485 busses and comprising: each of the control and the processing modules having: a first RS-485 transceiver connected to a first RS-485 bus; a second RS-485 transceiver connected to a second RS-485 bus; selector logic responsive to a control signal for selecting one of the first and the second busses to receive signals from and for transmitting the received signals to the respective module; and software logic executable on a baseboard management controller (BMC) chip, said software logic including control logic for monitoring the health of the respectively selected bus and for providing the control signal to the respective selector logic, wherein the control module delivers test signals within a predetermined time period on the first and second busses to test the electrical connectivity of each of the two busses, wherein the selector logic of the processing module monitors test signals received on the respectively selected bus and causes selection of a bus other than the respectively selected bus, if it does not receive test signals on the respectively selected bus within the predetermined time period; and wherein the test signals are able to cause a voltage difference on a healthy RS-485 bus to transit from a quiescent state to an active state in which the voltage difference represents a binary 0 or a binary 1 signal.