PXN20RM Datasheet, PDF (703/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

FlexRay Communication Controller (FlexRAY)
26.6.5.2 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 26.6.2.1, 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 26.6.2.1.2, Data Field Offset.
26.6.5.2.1 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 26-109. A detailed description is given in Table 26-85.
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 26-109. 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 26-110. A detailed description is given in Table 26-86. 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 26-110. Frame Header Structure (Transmit Message Buffer)
The structure of the frame header in the message buffer header field for transmit message buffers assigned
to key slot is given in Figure 26-111.
Freescale Semiconductor
PXN20 Microcontroller Reference Manual, Rev. 1
26-89