Freescale Semiconductor FlexRay MFR4310 - Figure 3-117. Receive Message Buffer Access Regions

FlexRay Module (FLEXRAYV4)
MFR4310 Reference Manual, Rev. 2
Freescale Semiconductor 161
Message Buffer Status Update after Null Frame Transmission
After the transmission of a null frame, the status of the message buffer that was used for the null frame
transmission is not changed at all. The slot status field is not updated, the status and control flags are not
changed, and the interrupt flag is not set.
3.4.6.3 Receive Message Buffers
The section provides a detailed description of the functionality of the receive message buffers.
A receive message buffer is used to receive a message from the FlexRay Bus based on individual filter
criteria. The FlexRay module uses the receive message buffer to provide the following data to the
application
1. message data received
2. information about the reception process
3. status information about the slot in which the message was received
A individual message buffer with message buffer number n is configured as a receive message buffer by
the following configuration settings
• MBCCSRn.MBT = 0 (single buffered message buffer)
• MBCCSRn.MTD = 0 (receive message buffer)
To certain message buffer fields, both the application and the FlexRay module have access. To ensure data
consistency, a message buffer locking scheme is implemented that is used to control the access to the data,
control, and status bits of a message buffer. The access regions for receive message buffers are depicted in
Figure 3-117. A description of the regions is given in Table 3-95. If an region is active as indicated in
Table 3-96, the access scheme given for that region applies to the message buffer.
Figure 3-117. Receive Message Buffer Access Regions
Message Buffer Data Field: DATA[0-N]
Message Buffer Header Field: Frame Header
MBCCSRn.DVAL/DUP
Message Buffer Header Field: Slot Status
Message Buffer Header Field: Data Field Offset
MBCCFRn.CHA/CHB/CCF*
MBFIDRn.FID
MBIDXRn.MBIDX
MBCCSRn.MTD
RX
SR
CFG
MSG