PXS20RM Datasheet, PDF (824/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

FlexRay Communication Controller
The message buffer data field is located in the FlexRay memory area; thus, the CC 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.
26.6.5.3.1 Message Buffer Data Field Read Access
For transmit message buffers, the CC will 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 (FR_MBIDXRn). While the
message buffer is locked, the CC will 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 (FR_RFARIR) or the Receive FIFO B Read Index Register (FR_RFBRIR) when the related
fill levels in the Receive FIFO Fill Level and POP Count Register (FR_RFFLPCR) indicate an non-empty
FIFO.
26.6.5.3.2 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 26-102.
Table 26-102. Frame Data Write Access Constraints
Field
DATA, MID, NMV
single buffered
POC:config or MB_DIS
or MB_LCK
double buffered
commit side
transmit side
POC:config or MB_DIS
or MB_LCK
POC:config or MB_DIS
Table 26-103. Frame Data Field Descriptions
Field
Description
DATA 0,
DATA 1,
...
DATA N-1
Message Data — Provides the message data received or to be transmitted.
For receive message buffer and receive FIFOs, this field provides the message data received for this
message buffer.
For transmit message buffers, the field provides the message data to be transmitted.
MID 0,
MID 1
Message Identifier — If the payload preamble bit PPI is set in the message buffer frame header, the MID
field holds the message ID of a dynamic frame located in the message buffer. The receive FIFO filter
uses the received message ID for message ID filtering.
NMV 0,
NMV 1,
...
NMV 11
Network Management Vector — If the payload preamble bit PPI is set in the message buffer frame
header, the network management vector field holds the network management vector of a static frame
located in the message buffer.
Note: The MID and NMV bytes replace the corresponding DATA bytes.
26-112
PXS20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor