Freescale Semiconductor FlexRay MFR4310 - Figure 3-108. Message Buffer Data Field Structure

FlexRay Module (FLEXRAYV4)
MFR4310 Reference Manual, Rev. 2
150 Freescale Semiconductor
NOTE
The FlexRay module does not access any locations outside the message
buffer data field boundaries given by Table 3-86.
Figure 3-108. Message Buffer Data Field Structure
The message buffer data field is located in the FRM; thus, the FlexRay module has no means to control
application write access to the field. To ensure data consistency, the application must follow a write and
read access scheme.
3.4.5.3.1 Message Buffer Data Field Read Access
For transmit message buffers, the FlexRay module does not modify the content of the Message Buffer Data
Field. Thus the application can read back the data at any time without any impact on data consistency.
For receive message buffers the application must lock the related receive message buffer and retrieve the
message buffer header index from the Message Buffer Index Registers (MBIDXRn). While the message
buffer is locked, the FlexRay module does not update the Message Buffer Data Field.
For receive FIFOs, the application can read the message buffer indicated by the Receive FIFO A Read
Index Register (RFARIR) or the Receive FIFO B Read Index Register (RFBRIR) when the related receive
FIFO non-empty interrupt flag FNEAIF or FNEBIF is set in the Global Interrupt Flag and Enable Register
(GIFER). While the non-empty interrupt flag is set, the FlexRay module does not update the Message
Buffer Data Field related to message buffer indicated by Receive FIFO A Read Index Register (RFARIR)
or the Receive FIFO B Read Index Register (RFBRIR).
3.4.5.3.2 Message Buffer Data Field Write Access
For receive message buffers, receive shadow buffers, and receive FIFOs, the application must not write to
the message buffer data field.
For transmit message buffers, the application must follow the write access restrictions given in Table 3-87.
Receive FIFO for channel B RFDSR.ENTRY_SIZE (RFSR.SEL = 1)
1514131211109876543210
0x0 DATA0 / MID0 / NMV0 DATA1 / MID1 / NMV1
0x2 DATA2 / NMV2 DATA3 / NMV3
... ... ...
0xN-2 DATA N-2 DATA N-1
Table 3-86. Message Buffer Data Field Minimum Length
physical message buffer
assigned to
minimum length defined by