PXD10RM Datasheet, PDF (676/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

The FlexCAN module stores CAN messages for transmission and reception using a Message Buffer
structure. 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
(0x80–0x8F space).
Table 18-3. Message Buffer MB0 Memory Mapping
Address Offset
0x80
0x84
0x88–0x8F
MB Field
Control and Status (C/S)
Identifier Field
Data Field 0 – Data Field 7 (1 byte each)
18.3.2 Message Buffer Structure
The Message Buffer structure used by the FlexCAN module is represented in Figure 18-2. Both Extended
and Standard Frames (29-bit Identifier and 11-bit Identifier, respectively) used in the CAN specification
(Version 2.0 Part B) are represented.
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 31
0x0
CODE
S ID RT LENGTH
RER
R
0x4 PRIO
ID (Standard/Extended)
0x8
Data Byte 0
Data Byte 1
0xC
Data Byte 4
Data Byte 5
TIME STAMP
ID (Extended)
Data Byte 2
Data Byte 6
Data Byte 3
Data Byte 7
= Unimplemented or Reserved
Figure 18-2. Message Buffer Structure
Table 18-4. Message Buffer Structure Field Descriptions
Field
CODE
SRR
Description
Message Buffer Code
This 4-bit field can be accessed (read or write) by the CPU and by the Flexcan module itself, as part
of the message buffer matching and arbitration process. The encoding is shown in Table 18-5 and
Table 18-6. See Section 18.4, Functional description for additional information.
Substitute Remote Request
Fixed 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. It
can be received as either recessive or dominant. If FlexCAN receives this bit as dominant, then it is
interpreted as arbitration loss.
1 = Recessive value is compulsory for transmission in Extended Format frames
0 = Dominant is not a valid value for transmission in Extended Format frames
18-6
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor