FlexRay Communication Controller (FLEXRAY)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
30-87
Preliminary
Figure 30-104. Frame Header Structure
Frame Header Section Access
The frame header is located in the FRM. To ensure data consistency, the application must follow the write
access scheme described below.
For receive message buffers, receive shadow buffers, and receive FIFOs, the application must not write to
the frame header field.
For transmit message buffers, the application must follow the write access restrictions given in
. This table shows the condition under which the application can write to the frame header
entries. In general, the application can modify all frame header entries when the protocol is in the
POC:config
state or when the message buffer is disabled. For message buffers assigned to the dynamic
segment, the application can modify all frame header entries except the frame ID when the message buffer
is locked.
The frame header entries NUF, SYF, SUF, and CYCCNT are not used for frame transmission. These values
are generated internally before frame transmission depending on the current transmission state and
configuration.
For transmit message buffers assigned to the
static
segment, the PLDLEN value must be equal to the value
of the payload_length_static field in the
Protocol Configuration Register 19 (PCR19)
fulfilled, the static payload length error flag SPL_EF in the
CHI Error Flag Register (CHIERFR)
is set
when the message buffer is under transmission. The PE generates a syntactically and semantically correct
frame with payload_length_static payload words and the payload length field in the frame header set to
payload_length_static.
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 for TX message buffers, not updated for RX message buffers
Table 30-82. Frame Header Write Access Constraints
Field
TX
Single Buffered
Double Buffered
Static
Segment
Dynamic
Segment
Static Segment
Dynamic Segment
Commit Side
Transmit Side
Commit Side
Transmit Side
FID
POC:config
or MB_DIS
R*, PPI
NUF, SYF
SUF
CYCCNT
PLDLEN
HDCRD
POC:config
or
MB_DIS
POC:config
or
MB_DIS
or
MB_LCK
POC:config
or
MB_DIS
POC:config
or
MB_DIS
or
MB_LCK
POC:config
or
MB_DIS