RM0029 Datasheet, PDF (1558/1740 Pages) STMicroelectronics – The primary objective of this document

FlexRay Communication Controller (FlexRay)
RM0029
Message buffer header field description
This section provides a detailed description of the usage and content of the message buffer
header field. A description of the structure of the message buffer header fields is given in
Section , Message buffer header field. Each message buffer header field consists of three
sections: the frame header section, the data field offset, and the slot status section. For a
detailed description of the Data Field Offset, see Section , Data field offset.
Frame header description
Frame header content
The semantic and content of the frame header section depends on the message buffer type.
For individual receive message buffers and receive FIFOs, the frame header receives the
frame header data of the first valid frame received on the assigned channels.
For receive shadow buffers, the frame header receives the frame header data of the current
frame received regardless of whether the frame is valid or not.
For transmit message buffers, the application writes the frame header of the frame to be
transmitted into this location. The frame header will be read out when the frame is
transferred to the FlexRay bus.
The structure of the frame header in the message buffer header field for receive message
buffers and the receive FIFO is given in Figure 945. A detailed description is given in
Table 877.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0x0 R PPI NUF SYF SUF
FID
0x2 0 0
CYCCNT
0
PLDLEN
0x4 0 0 0 0 0
HDCRC
Figure 945. Frame header structure (receive message buffer and receive FIFO)
The structure of the frame header in the message buffer header field for transmit message
buffers is given in Figure 946. A detailed description is given in Table 878. The checks that
will be performed are described in Frame header checks.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0x0 R PPI NUF SYF SUF
FID
0x2
CYCCNT
PLDLEN
0x4
HDCRC
= not used
= checked
= checked if static slot
Figure 946. Frame header structure (transmit message buffer)
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