FlexCANMPC5606S Microcontroller Reference Manual, Rev. 7674 Freescale SemiconductorThe FlexCAN module stores CAN messages for transmission and reception using a Message Bufferstructure. Each individual MB is formed by 16 bytes mapped on memory as described in Table 18-3.Table 18-3 shows a Standard/Extended Message Buffer (MB0) memory map, using 16 bytes total space(0x80–0x8F).18.3.2 Message Buffer structureThe Message Buffer structure used by the FlexCAN module is represented in Figure 18-2. Both Extendedand Standard frames (29-bit identifier and 11-bit identifier, respectively) used in the CAN specification(Version 2.0 Part B) are represented.Table 18-3. Message Buffer MB0 memory mappingAddress offset MB field0x80 Control and Status (C/S)0x84 Identifier Field0x88–0x8F Data Field 0–Data Field 7 (1 byte each)0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 310x0CODESRRIDERTRLENGTH TIME STAMP0x4 PRIO ID (Standard/Extended) ID (Extended)0x8 Data Byte 0 Data Byte 1 Data Byte 2 Data Byte 30xC Data Byte 4 Data Byte 5 Data Byte 6 Data Byte 7Figure 18-2. Message Buffer StructureTable 18-4. Message Buffer Structure field descriptionsField DescriptionCODE Message Buffer CodeThis 4-bit field can be accessed (read or write) by the CPU and by the Flexcan module itself, as partof the message buffer matching and arbitration process. The encoding is shown in Table 18-5 andTable 18-6. See Section 18.4, Functional description for additional information.SRR Substitute Remote RequestFixed recessive bit, used only in extended format. It must be set to 1 by the user for transmission(Tx Buffers) and will be stored with the value received on the CAN bus for Rx receiving buffers. Itcan be received as either recessive or dominant. If FlexCAN receives this bit as dominant, then it isinterpreted as arbitration loss.0 Dominant is not a valid value for transmission in Extended Format frames1 Recessive value is compulsory for transmission in Extended Format framesIDE ID Extended BitThis bit identifies whether the frame format is standard or extended.0 Frame format is standard1 Frame format is extended
