Vehicle communications network transceiver, bus driver therefor

Abstract

A transceiver device for use with a microcontroller and a symbol encoder decoder device (forming a node in a communications network) for transmitting and receiving variable pulse width modulated (VPWM) analog signals containing symbol messages over a communications bus. The transceiver accepts digital VPWM signals from the symbol encoder decoder device which were generated by the microcontroller and converts the digital signals into VPWM analog signals and then transmits the analog signal over the bus to other nodes. The transceiver also receives VPWM analog signals placed on the bus by other nodes of the network and transfers the signals in digital form to the symbol encoder decoder device which, in turn, communicates the decoded messages to the microcontroller. The transceiver contains a ground translation circuit for transferring transmitted signals to an independent bus ground return before a bus driver circuit sources message signals in the form of pulse currents over the bus. The bus driver circuit contains circuits that permit arbitration to take place when more than one node attempts to transmit over the bus. The receiver circuit also contains ground translation circuits for translating bus signals from the bus ground return to a signal ground return.