Message RAM
32 bit
Header MB0
Data MB0
Header Partition
Header MB1
Data Partition
Header MBn
Data MB1
unused
2048
words
‚
‚
‚
‚
‚
‚
Data MBn
Module Operation
1259
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
FlexRay Module
Figure 26-23. Configuration Example of Message Buffers in the Message RAM
Header Partition
Stores header segments of FlexRay frames:
•
Supports a maximum of 128 message buffers
•
Each message buffer has a header of four 32 bit words
•
Header 3 of each message buffer holds the 11-bit data pointer to the corresponding data section in the
data partition
Data Partition
Flexible storage of data sections with different length. Some maximum values are:
•
30 message buffers with 254 byte data section each
•
Or 56 message buffers with 128 byte data section each
•
Or 128 message buffers with 48 byte data section each
Restriction:
header par data partition may not occupy more than 2048 x 32 bit words.
26.2.13.1.1 Header Partition
The elements used for configuration of a message buffer as well as the current message buffer status are
stored in the header partition of the message RAM as shown in
. Configuration of the header
sections of the message buffers is done through IBF (Write Header Section 1,2,3). Read access to the
header sections is done through OBF (read header section 1,2,3 + message buffer status). The data
pointer has to be calculated by the programmer to define the starting point of the data section for the
corresponding message buffer in the data partition of the message RAM. The data pointer should not be
modified during runtime. For message buffers belonging to the receive FIFO (re)configuration should be
done in DEFAULT_CONFIG or CONFIG state only.
The header section of each message buffer occupies four 32 bit words in the header partition of the
message RAM. The header of message buffer 0 starts with the first word in the message RAM.
For transmit buffers the Header CRC has to be calculated by the host CPU.