PXS20RM Datasheet, PDF (807/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

FlexRay Communication Controller
26.6.2.1.2 Data Field Offset
The data field offset follows the frame header in the message buffer data field and occupies two bytes. It
contains the offset of the corresponding message buffer data field with respect to the CC FlexRay memory
area base address as provided by SMBA field in the System Memory Base Address Register
(FR_SYMBADR). The data field offset is used to determine the start address SADR_MBDF of the
corresponding message buffer data field in the FlexRay memory area according to Equation 26-2.
SADR_MBDF = [Data Field Offset] + SMBA
Eqn. 26-2
26.6.2.1.3 Slot Status
The slot status occupies the last two bytes of the message buffer header field. It provides the slot and frame
status related information according to the FlexRay Communications System Protocol Specification,
Version 2.1 Rev A. A detailed description of the content and usage of the slot status is provided in
Section 26.6.5.2.3, Slot Status Description.
26.6.2.2 Message Buffer Data Field
The message buffer data field is a contiguous area of 2-byte entities. This field contains the frame payload
data, or a part of it, of the frame to be transmitted to or received from the FlexRay bus. The minimum
length of this field depends on the specific message buffer configuration and is specified in the message
buffer descriptions given in Section 26.6.3, Message Buffer Types.
26.6.3 Message Buffer Types
The CC provides three different types of message buffers.
• Individual Message Buffers
• Receive Shadow Buffers
• Receive FIFO Buffers
For each message buffer type the structure of the physical message buffer is identical. The message buffer
types differ only in the structure and content of message buffer control data, which control the related
physical message buffer. The message buffer control data are described in the following sections.
26.6.3.1 Individual Message Buffers
The individual message buffers are used for all types of frame transmission and for dedicated frame
reception based on individual filter settings for each message buffer. The CC supports three types of
individual message buffers, which are described in Section 26.6.6, Individual Message Buffer Functional
Description.
Each individual message buffer consists of two parts, the physical message buffer, which is located in the
FlexRay memory area, and the message buffer control data, which are located in dedicated registers. The
structure of an individual message buffer is given in Figure 26-114.
Each individual message buffer has a message buffer number n assigned, which determines the set of
message buffer control registers associated to this individual message buffer. The individual message
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PXS20 Microcontroller Reference Manual, Rev. 1
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