Freescale Semiconductor FlexRay MFR4310 - Functional Description; Message Buffer Concept; Physical Message Buffer; Figure 3-96. Physical Message Buffer Structure

FlexRay Module (FLEXRAYV4)
MFR4310 Reference Manual, Rev. 2
134 Freescale Semiconductor
3.4 Functional Description
This section provides a detailed description of the functionality implemented in the FlexRay module.
3.4.1 Message Buffer Concept
The FlexRay module uses a data structure called message buffer to store frame data, configuration, control,
and status data. Each message buffer consists of two parts, the message buffer control data and the physical
message buffer. The message buffer control data are located in dedicated registers. The structure of the
message buffer control data depends on the message buffer type and is described in Section 3.4.3,
“Message Buffer Types”. The physical message buffer is located in the FRM and is described in
Section 3.4.2, “Physical Message Buffer”.
3.4.2 Physical Message Buffer
All FlexRay messages and related frame and slot status information of received frames and of frames to
be transmitted to the FlexRay bus are stored in data structures called physical message buffers. The
physical message buffers are located in the FRM.The structure of a physical message buffer is depicted in
Figure 3-96.
A physical message buffer consists of two fields, the message buffer header field and the message buffer
data field. The message buffer header field contains the frame header, the data field offset, and the slot
status.The message buffer data field contains the frame data.
The connection between the two fields is established by the data field offset.
Figure 3-96. Physical Message Buffer Structure
3.4.2.1 Message Buffer Header Field
The message buffer header field is a contiguous region in the FRM and occupies ten bytes. It contains the
frame header, the data field offset, and the slot status. Its structure is shown in Figure 3-96. The physical
start address
SADR_MBHF of the message buffer header field must be 16-bit aligned.
3.4.2.1.1 Frame Header
The frame header occupies the first six bytes in the message buffer header field. It contains all FlexRay
frame header related information according to the FlexRay Communications System Protocol
Data Field Offset
Frame Data
Message Buffer Header Field
Message Buffer Data Field
Slot StatusFrame Header
SADR_MBDF
SADR_MBHF
FlexRay Memory