DS791 Datasheet, PDF (26/46 Pages) Xilinx, Inc – LogiCORE IP AXI Controller

LogiCORE IP AXI Controller Area Network (axi_can) (v1.03.a)
Writes to TX FIFO and High Priority TX Buffer
When writing to the TX FIFO or the TX HPB, all 16 bytes must be written. The first word written (4 bytes) is the
Identifier (IDR). The second word written is the DLC field (DLCR). The third word written is Data Word 1 (DW1R)
and the fourth word written is Data Word 2 (DW2R).
When transmitting on the CAN bus, the CAN controller transmits the data bytes in the following order (DB0, DB1,
DB2, DB3, DB4, DB5, DB6, DB7). The MSB of a data byte is transmitted first.
All four words must be written for each message, including messages containing fewer than 8 data bytes. Reads
transactions from the TX FIFO or the TX High Priority Buffer return '0's.
• '0's must be written to Data Fields in DW1R and DW2R registers that are not used
• '0's must be written to bits 4 to 31 in the DLCR
• '0's must be written to IDR [13 to 31] for standard frames
Identifier
The Identifier (IDR) word contains the identifier field of the CAN message. Two different formats exist for the
Identifier field of the CAN message frame: Standard and Extended frames.
• Standard Frames: Standard frames have an 11-bit identifier field called the Standard Identifier.Only the
ID[28..18], SRR/RTR, and IDE bits are valid. ID[28..18] is the 11 bit identifier. The SRR/RTR bit differentiates
between data and remote frames. IDE is '0' for standard frames. The other bit fields are not used.
• Extended Frames: Extended frames have an 18-bit identifier extension in addition to the Standard Identifier.
All bit fields are valid. The RTR bit is used to differentiate between data and remote frames (The SRR/RTR bit
and IDE bit are both '1' for all Extended Frames).
Table 31 provides bit descriptions for the Identifier Word. Table 32 provides bit descriptions for the DLC Word.
Table 33 provides bit descriptions for Data Word 1 and Data Word 2
DS791 June 22, 2011
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Product Specification