NXP Semiconductors MPC5644A, Reference Manual, Page: 1552 / 1735

FlexRay Communication Controller (FlexRay)
MPC5644A Microcontroller Reference Manual, Rev. 6
1552 Freescale Semiconductor
The application configures the number of utilized individual message buffers by writing the message
buffer number of the last utilized message buffer into the LAST_MB_UTIL field in the
Message Buffer
Segment Size and Utilization Register (FR_MBSSUTR) .
The application configures the size of the two segments of individual message buffers by writing the
message buffer number of the last message buffer in the first segment into the LAST_MB_SEG1 field in
the
Message Buffer Segment Size and Utilization Register (FR_MBSSUTR)
The application configures the length of the message buffer data fields for both of the message buffer
segments by writing to the MBSEG2DS and MBSEG1DS fields in the
Message Buffer Data Size Register
(FR_MBDSR) .
Depending on the current receive functionality of the CC, the application must configure the receive
shadow buffers. For each segment and for each channel with at least one individual receive message buffer
assigned, the application must configure the related receive shadow buffer using the
Receive Shadow
Buffer Index Register (FR_RSBIR) .
33.6.6.1.2 Specific configuration data
The second part of the message buffer configuration data is specific for each message buffer.
These data can be changed only when either
• the protocol is in the POC:config state or
• the message buffer is disabled, that is, FR_MBCCSRn[EDS] = 0
The individual message buffer type is defined by the MTD and MBT bits in the Message Buffer
Configuration, Control, Status Registers (FR_MBCCSRn) as given in Table 33-104 .
The message buffer specific configuration data are
1. MCM, MBT, MTD bits in Message Buffer Configuration, Control, Status Registers
(FR_MBCCSRn)
2. all fields and bits in Message Buffer Cycle Counter Filter Registers (FR_MBCCFRn)
3. all fields and bits in Message Buffer Frame ID Registers (FR_MBFIDRn)
4. all fields and bits in Message Buffer Index Registers (FR_MBIDXRn)
Table 33-104. Individual message buffer types
FR_MBCCSRn
Individual message buffer description
MTD MBT
0 0 Receive Message Buffer
0 1 Reserved
1 0 Single Transmit Message Buffer
1 1 Double Transmit Message Buffer