MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
22-6
Freescale Semiconductor
The FlexCAN2 module stores CAN messages for transmission and reception using a message buffer
structure. Each individual MB is formed by 16 bytes mapped in memory as described in
FlexCAN2 module can manage up to 64 message buffers.
shows a standard/extended message
buffer (MB0) memory map, using 16 bytes (0x80
–
0x8F) total space.
NOTE
Reading the C/S word of a message buffer (the first word of each MB) will
lock it, preventing it from receiving further messages until it is unlocked
either by reading another MB or by reading the timer.
22.3.2
Message Buffer Structure
The message buffer structure used by the FlexCAN2 module is represented in
and standard frames (29-bit identifier and 11-bit identifier, respectively) used in the CAN specification
(version 2.0 Part B) are represented.
Base + 0x0060–
Base + 0x007F
—
Reserved
—
Base + 0x0080–
Base + 0x017F
MB0–MB15
Message buffers 0–15
128 bits
per MB
Base + 0x0180–
Base + 0x027F
MB16–MB31
Message buffers 16–31
128 bits
per MB
Base + 0x0280–
Base + 0x047F
MB32–MB63
Message buffers 32–63
128 bits
per MB
1
The MPC5554 has FlexCAN2 modules A, B, and C, whereas the MPC5553 only has FlexCAN2 modules A and C.
Table 22-3. Message Buffer MB0 Memory Mapping
Address
Offset
MB Field
0x80
Control and Status (C/S)
0x84
Identifier Field
0x88–0x8F
Data fields 0–7 (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 31
0x0
CODE
SRR
IDE
RT
R
LENGTH
TIME STAMP
0x4
ID (Extended/Standard)
ID (Extended)
0x8
Data Byte 0
Data Byte 1
Data Byte 2
Data Byte 3
0xC
Data Byte 4
Data Byte 5
Data Byte 6
Data Byte 7
Figure 22-2. Message Buffer Structure
Table 22-2. Module Memory Map (Continued)
Summary of Contents for MPC5553
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