Transmit pre-arbitration scheme for a can device and a can device that implements this scheme

Abstract

In a CAN device, e.g., a CAN microcontroller, that supports a plurality of message objects, a method that includes concurrently staging two or more transmit messages associated with respective ones of two or more enabled transmit message objects for attempted transmission over a CAN bus coupled to the CAN device, and performing a pre-arbitration process to determine which of the two or more concurrently staged transmit messages has priority. The message determined to have priority is deemed a winning message and the message object associated with the winning message is deemed a winning message object. In a presently preferred embodiment, the pre-arbitration process is a selected one of at least two pre-arbitration schemes, including a first pre-arbitration scheme whereby priority is determined according to a CAN bus arbitration priority scheme established by the governing CAN protocol, and a second pre-arbitration scheme whereby priority is determined by selecting the transmit message associated with the highest-numbered (or, alternatively, lowest-numbered) message object as the winning message. In the event that more than one of the two or more concurrently staged transmit messages are determined to have the same priority, the transmit message associated with the highest-numbered message object is designated as the winning message. The method further includes attempting to transmit the winning message over the CAN bus. If the winning message is not granted access to the CAN bus, the pre-arbitration priority determination process is repeated.