FlexRay Communication Controller (FlexRAY)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 26-99
The message buffer specific configuration data are
1. MCM, MBT, MTD bits in Message Buffer Configuration, Control, Status Registers (MBCCSRn)
2. all fields and bits in Message Buffer Cycle Counter Filter Registers (MBCCFRn)
3. all fields and bits in Message Buffer Frame ID Registers (MBFIDRn)
4. all fields and bits in Message Buffer Index Registers (MBIDXRn)
The meaning of the specific configuration data depends on the message buffer type, as given in the detailed
message buffer type descriptions Section 26.6.6.2, Single Transmit Message Buffers, Section 26.6.6.3,
Receive Message Buffers, and Section 26.6.6.4, Double Transmit Message Buffer.
26.6.6.2 Single Transmit Message Buffers
The section provides a detailed description of the functionality of single buffered transmit message buffers.
A single transmit message buffer is used by the application to provide message data to the controller that
will be transmitted over the FlexRay Bus. The controller uses the transmit message buffers to provide
information about the transmission process and status information about the slot in which message was
transmitted.
The individual message buffer with message buffer number n is configured to be a single transmit message
buffer by the following settings:
• MBCCSRn[MBT] = 0 (single buffered message buffer)
• MBCCSRn[MTD] = 1 (transmit message buffer)
26.6.6.2.1 Access Regions
To certain message buffer fields, both the application and the controller have access. To ensure data
consistency, a message buffer locking scheme is implemented, which is used to control the access to the
data, control, and status bits of a message buffer. The access regions for single transmit message buffers
are depicted in Figure 26-119. A description of the regions is given in Table 26-95. If an region is active
as indicated in Table 26-96, the access scheme given for that region applies to the message buffer.
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