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Chapter 13 FlexRay Communication Controller (FLEXRAY)
MC9S12XF - Family Reference Manual, Rev.1.19
542
Freescale Semiconductor
Each individual message buffer consists of two parts, the physical message buffer, which is located in the
FRM, and the message buffer control data, which are located in dedicated registers. The structure of an
Each individual message buffer has a message buffer number n assigned, which determines the set of
message buffer control registers associated to this individual message buffer. The individual message
buffer with message buffer number n is controlled by the registers MBCCSRn, MBCCFRn, MBFIDRn,
and MBIDXRn.
The connection between the message buffer control registers and the physical message buffer is
The start address SADR_MBHF of the related message buffer header eld in the FRM is determined
SADR_MBHF = (MBIDXRn[MBIDX] * 10) + SYS_MEM_BASE_ADDR
Eqn. 13-3
Figure 13-101. Individual Message Buffer Structure
13.6.3.1.1
Individual Message Buffer Segments
The set of the individual message buffers can be split up into two message buffer segments using the
a message buffer number n <= MBSSUTR.LAST_MB_SEG1 belong to the rst message buffer segment.
All individual message buffers with a message buffer number n > MBSSUTR.LAST_MB_SEG1 belong
to the second message buffer segment. The following rules apply to the length of the message buffer data
eld:
all physical message buffers associated to individual message buffers that belong to the same
message buffer segment must have message buffer data elds of the same length
the minimum length of the message buffer data eld for individual message buffers in the rst
message buffer segment is 2 * MBDSR.MBSEG1DS bytes
the minimum length of the message buffer data eld for individual message buffers assigned to the
second segment is 2 * MBDSR.MBSEG2DS bytes.
MBFIDRn
Message Buffer Control Registers
MBCCSRn
MBCCFRn
MBIDXRn
(min) MBDSR[MBSEG1DS] * 2 bytes / MBDSR[MBSEG2DS] * 2 bytes
Data Field Offset
Frame Data
Message Buffer Header Field
Message Buffer Data Field
Slot Status
Frame Header
SADR_MBDF
SADR_MBHF
System
Memor
y