Freescale Semiconductor FlexRay MFR4310 - Figure 3-101. Frame Header Structure; Table 3-80. Frame Header Write Access Constraints

FlexRay Module (FLEXRAYV4)
MFR4310 Reference Manual, Rev. 2
Freescale Semiconductor 143
Figure 3-101. 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 Table 3-80.
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). If this is not
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.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
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 3-80. 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