4 functional overview, 1 transmit process, 4 functional overview -8 – Motorola ColdFire MCF5281 User Manual
Page 478: 1 transmit process -8
FlexCAN
25-8
Freescale Semiconductor
Figure 25-5. FlexCAN Memory Map
25.4
Functional Overview
The FlexCAN module is flexible in that each one of its 16 message buffers (MBs) can be assigned either
as a transmit buffer or a receive buffer. Each MB, which is up to 8 bytes long, is also assigned an interrupt
flag bit that indicates successful completion of either transmission or reception.
NOTE
Note that for both processes, the first CPU action in preparing a MB should
be to deactivate it by setting its code field to the proper value. This
requirement is mandatory to assure proper operation.
25.4.1
Transmit Process
The CPU prepares or changes an MB for transmission by executing the following steps:
•
Writing the Control/Status word to hold Tx MB inactive (code = 1000).
•
Writing the ID_HIGH and ID_LOW words.
ID_HIGH
ID_LOW
Control/Status
Reserved
8 bytes Data field
0x80-0x8F
0x82
0x84
0x86
Message Buffer 0
Message Buffer 1
Message Buffer 2
Message Buffer 15
0x8C
0x90
0xA0
0x170
Message Buffers
0x8E
0x17E
0x9E
0xAE
0xB0
0x16E
FlexCAN Base
Address Offset
Message Buffer 3
through
Message Buffer 14
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3