FlexRay Communication Controller (FLEXRAY)
22-76
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
22.6
Functional Description
This section provides a detailed description of the functionality implemented in the controller.
22.6.1
Message Buffer Concept
The controller 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
. The physical message buffer is located in the flexray memory and is described in
Section 22.6.2, Physical Message Buffer
22.6.2
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 flexray memory.The structure of a physical message buffer is
depicted in
.
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 22-103. Physical Message Buffer Structure
22.6.2.1
Message Buffer Header Field
The message buffer header field is a contiguous region in the flexray memory and occupies ten bytes. It
contains the frame header, the data field offset, and the slot status. Its structure is shown in
The physical start address
SADR_MBHF
of the message buffer header field must be 16-bit aligned.
22.6.2.1.1
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 Status
Frame Header
SADR_MBDF
SADR_MBHF
Fle
x
Ra
y Memor
y
Summary of Contents for PXR4030
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