Freescale Semiconductor FlexRay MFR4310 - Figure 3-120. Double Transmit Buffer Structure and Data Flow; Figure 3-121. Double Transmit Message Buffer Access Regions Layout

FlexRay Module (FLEXRAYV4)
MFR4310 Reference Manual, Rev. 2
168 Freescale Semiconductor
FlexRay module to transmit the message data to the FlexRay bus. The two sides are located in adjacent
individual message buffers. The message buffer that implements the commit side has an even message
buffer number 2n. The transmit side message buffer follows the commit side message buffer and has the
message buffer number 2n+1. The basic structure and data flow of a double transmit message buffer is
given in Figure 3-120.
Figure 3-120. Double Transmit Buffer Structure and Data Flow
NOTE
Both the commit and the transmit side must be configured with identical
values except for the Message Buffer Index Registers (MBIDXRn).
3.4.6.4.1 Access Regions
To certain message buffer fields, both the application and the FlexRay module have access. To ensure data
consistency, a message buffer locking scheme is implemented, which controls the exclusive access to the
data, control, and status bits of the message buffer.
The access scheme for double transmit message buffers is depicted in Figure 3-121. The given regions
represent fields that can be accessed from both the application and the FlexRay module and, thus, require
access restrictions. A description of the regions is given in Table 3-101.
Figure 3-121. Double Transmit Message Buffer Access Regions Layout
Commit Side Transmit Side
Application FlexRay Bus
MB# 2n
MB# 2n+1
Internal Message
Transfer
message data message data message data
Message Buffer Data Field: DATA[0-N]
Message Buffer Header Field: Frame Header
MBCCSR[2n]n.CMT
Message Buffer Header Field: Slot Status
Message Buffer Header Field: Data Field Offset
MBCCFR[2n].MTM/CHA/CHB/CCF*
MBFIDR[2n].FID
MBIDXR[2n].MBIDX
MBCCSR[2n].MBT/MTD
Message Buffer Data Field: DATA[0-N]
Message Buffer Header Field: Frame Header
MBCCSR[2n+1].CMT
Message Buffer Header Field: Slot Status
Message Buffer Header Field: Data Field Offset
MBCCFR[2n+1].MTM/CHA/CHB/CCF*
MBFIDR[2n+1].FID
MBIDXR[2n+1].MBIDX
MBCCSR[2n+1].MBT/MTD
Commit Side Transmit Side
CFG
MSG
CFG
ITX
SS
SS
SR
TX