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Chapter 13 FlexRay Communication Controller (FLEXRAY)
MC9S12XF - Family Reference Manual, Rev.1.19
Freescale Semiconductor
557
13.6.6
Individual Message Buffer Functional Description
The FlexRay block provides three basic types of individual message buffers:
1. Single Transmit Message Buffers
2. Double Transmit Message Buffers
3. Receive Message Buffers
Before an individual message buffer can be used, it must be congured by the application. After the initial
conguration, the message buffer can be recongured later. The set of the conguration data for individual
13.6.6.1
Individual Message Buffer Conguration
The individual message buffer conguration consists of two steps. The rst step is the allocation of the
required amount of memory for the FRM. The second step is the programming of the message buffer
conguration registers, which is described in this section.
13.6.6.1.1
Common Conguration Data
One part of the message buffer conguration data is common to all individual message buffers and the
receive shadow buffers. These data can only be set when the protocol is in the POC:cong state.
The application congures the number of utilized individual message buffers by writing the message
buffer number of the last utilized message buffer into the LAST_MB_UTIL eld in the
Message BufferTable 13-90. Frame Data Write Access Constraints
Field
single buffered
double buffered
commit side
transmit side
DATA, MID, NMV POC:cong or MB_DIS
or MB_LCK
POC:cong or MB_DIS
or MB_LCK
POC:cong or MB_DIS
Table 13-91. Frame Data Field Descriptions
Field
Description
DATA[0:N-1] Message Data — Provides the message data received or to be transmitted.
For receive message buffer and receive FIFOs, this eld provides the message data received for this message
buffer.
For transmit message buffers, the eld provides the message data to be transmitted.
MID[0:1]
Message Identier — If the payload preamble bit PPI is set in the message buffer frame header, the MID eld
holds the message ID of a dynamic frame located in the message buffer. The receive FIFO lter uses the
received message ID for message ID ltering.
NMV[0:11]
Network Management Vector — If the payload preamble bit PPI is set in the message buffer frame header, the
network management vector eld 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.