Method for writing back message id information to a match id register and a can microcontroller that implements this method

Abstract

A method for acceptance filtering incoming CAN frames, in a CAN device that provides a plurality of message objects each of which has an associated message buffer, at least one associated match ID register, and at least one associated mask register. The method includes the steps of extracting a multi-bit screener ID field from a received CAN frame, and then comparing the extracted screener ID field to a respective, user-specified multi-bit match ID field stored in the at least one match ID register associated with each enabled one of the message objects designated to be a receive message object, wherein the at least one mask register associated with each enabled message object designated to be a receive message object stores a user-specified, multi-bit mask field that masks selected bits of the corresponding match ID field, the masked bits being excluded from the comparisons. If a match is found as a result of the comparing step, data bytes of the received CAN frame are stored in the message buffer associated with the matching message object, and the extracted screener ID field is written into the at least one match ID register associated with the matching message object to replace the match ID field associated with the matching message object. The extracted screener ID field is not stored in the message buffer associated with the matching message object.