A method for setting CAN filter of Freescale MCU

Abstract

The invention discloses a CAN filter setting method about a Freescale semiconductor. The method comprises OR operation and three steps of step 1, carrying out OR operation and extracting a 0bit: firstly, carrying out OR operation on to-be-compared bits, extracting all bits corresponding to 0, and setting the bits into 1 through the variable i; step 2, carrying out ID negation and extracting 1bits: carrying out negation OR operation on each ID, extracting all bits corresponding to 1 and setting the bits into 1; and step 3, setting registers: obtaining all data corresponding to bits in the same bits and setting corresponding registers through m. According to the invention, ID negation is set, so the setting speed is fast, programming efficiency is greatly improved, manual operation errors are reduced, the structure is simple and clear, operation is simple, setting steps are few; and following upgrading and maintenance of the software are facilitated.

Description

technical field [0001] The invention relates to the technical field of computer programming, in particular to a CAN filter setting method of a Freescale single-chip microcomputer. Background technique [0002] The CAN module of the Freescale MCU needs to compare each bit carefully in setting the filter. For example, the single-chip microcomputer needs to accept CAN standard frames whose IDs are 0x21, 0x57, and 0x43. In the previous setting process, it is necessary to manually list each ID and compare each bit carefully to find out the bit with the same bit, and then set the obtained data. To the response register, to implement the CAN protocol version, standard and extended data frames and 0-8 byte data length are required, and a programmable bit rate up to 1MB / s is required, and remote frames are supported. CAN has 5 FIFO storage mechanisms Receive buffers, three transmit buffers with internal prioritization using local priority concept, programmable wake-up function with ...

AI Technical Summary

Problems solved by technology

For example, the single-chip microcomputer needs to accept CAN standard frames whose IDs are 0x21, 0x57, and 0x43. In the previous setting process, it is necessary to manually list each ID and compare each bit carefully to find out the bit with the same bit, and then set the obtained data. To the response register, to implement the CAN protocol version, standard and extended data frames and 0-8 byte data length are required, and a programmable bit rate up to 1MB / s is required, and remote frames are supported. CAN has 5 FIFO storage mechanisms Receive buffers, three transmit buffers with internal prioritization using local priority concept, programmable wake-up function with integrated low-pass filter, programmable loopback mode for self-test operation, programmable listen mode for CAN Bus monitoring, the internal timer provides time stamps for received and sent messages, three low-power modes: sleep, shutdown, MSCAN enable and other module features, but the current CAN filter setting circuit is not simple enough, and the setting steps are complicated

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